(Recent) `nano` packages in Ubuntu come with some `.nanorc` files preinstalled.

jline's `NanorcParser` sadly fails parsing `/usr/share/nano/json.nanorc` that comes with Ubuntu's package.

In particular, it fails at this line in `/usr/share/nano/json.nanorc`:
```
color brightblue "[][]"
```
with the exception
```
java.util.regex.PatternSyntaxException: Unclosed character class near index 3
[][]
   ^
...
	at org.jline.builtins.SyntaxHighlighter$NanorcParser.doPattern(SyntaxHighlighter.java:696)
...
```

Fixes jline#1156

(Recent) `nano` packages in Ubuntu come with some `.nanorc` files preinstalled.

jline's `NanorcParser` sadly fails parsing a couple of the regular expressions.

This change translates the regular expressions to Java regular expressions.

The differences are described in `org.jline.builtins.SyntaxHighlighter#posixToJavaRegex`:
* The first `]` in a bracket expression does not need to be escaped in Posix,translate to `\]`.
* Same as above for a negating bracket expression like `[^][]`, translate to `[^\]\[]`.
* Any `[` in a bracket expression does not need to be escaped in Posix, translate to `\[`.
* Any `]` not in a bracket expression is valid in both Posix and Java, no translation.
* A backslash before the closing bracket like `[.f\]` is not an escape of the closing bracket, the backslash needs to be escaped for Java, translate to `[.f\\]`.
* Do not perform the above translations within an escape via `\`.
* Do not perform the above translations for Posix "classes" like `[[:word:]]` or `[[:digit:]]` and their negation `[-[:word]]`.
* Do not perform the above translations for single-bracket Posix classes like `[:digit:]`, and handle the case of single-bracket Posix classes inside bracket expressions, like `[[:digit:]-.]`.

Test cases have been added.

There are however two regexes that still don't work, but those look invalid. To let jnano not trip over these, any `PatternSyntaxException` lets jnano just ignore the particular rule. A warning is logged in such cases.

Fixes jline#1156

(Recent) `nano` packages in Ubuntu come with some `.nanorc` files preinstalled.

jline's `NanorcParser` sadly fails parsing a couple of the regular expressions.

This change translates the regular expressions to Java regular expressions.

The differences are described in `org.jline.builtins.SyntaxHighlighter#posixToJavaRegex`:
* The first `]` in a bracket expression does not need to be escaped in Posix,translate to `\]`.
* Same as above for a negating bracket expression like `[^][]`, translate to `[^\]\[]`.
* Any `[` in a bracket expression does not need to be escaped in Posix, translate to `\[`.
* Any `]` not in a bracket expression is valid in both Posix and Java, no translation.
* A backslash before the closing bracket like `[.f\]` is not an escape of the closing bracket, the backslash needs to be escaped for Java, translate to `[.f\\]`.
* Do not perform the above translations within an escape via `\`.
* Do not perform the above translations for Posix "classes" like `[[:word:]]` or `[[:digit:]]` and their negation `[-[:word]]`.
* Do not perform the above translations for single-bracket Posix classes like `[:digit:]`, and handle the case of single-bracket Posix classes inside bracket expressions, like `[[:digit:]-.]`.

Test cases have been added.

There are however two regexes that still don't work, but those look invalid. To let jnano not trip over these, any `PatternSyntaxException` lets jnano just ignore the particular rule. A warning is logged in such cases.

Fixes jline#1156

(Recent) `nano` packages in Ubuntu come with some `.nanorc` files preinstalled.

jline's `NanorcParser` sadly fails parsing a couple of the regular expressions.

This change translates the regular expressions to Java regular expressions.

The differences are described in `org.jline.builtins.SyntaxHighlighter#posixToJavaRegex`:
* The first `]` in a bracket expression does not need to be escaped in Posix,translate to `\]`.
* Same as above for a negating bracket expression like `[^][]`, translate to `[^\]\[]`.
* Any `[` in a bracket expression does not need to be escaped in Posix, translate to `\[`.
* Any `]` not in a bracket expression is valid in both Posix and Java, no translation.
* A backslash before the closing bracket like `[.f\]` is not an escape of the closing bracket, the backslash needs to be escaped for Java, translate to `[.f\\]`.
* Do not perform the above translations within an escape via `\`.
* Do not perform the above translations for Posix "classes" like `[[:word:]]` or `[[:digit:]]` and their negation `[-[:word]]`.
* Do not perform the above translations for single-bracket Posix classes like `[:digit:]`, and handle the case of single-bracket Posix classes inside bracket expressions, like `[[:digit:]-.]`.

Test cases have been added.

There are however two regexes that still don't work, but those look invalid. To let jnano not trip over these, any `PatternSyntaxException` lets jnano just ignore the particular rule. A warning is logged in such cases.

Fixes jline#1156

(Recent) `nano` packages in Ubuntu come with some `.nanorc` files preinstalled.

jline's `NanorcParser` sadly fails parsing a couple of the regular expressions.

This change translates the regular expressions to Java regular expressions.

The differences are described in `org.jline.builtins.SyntaxHighlighter#posixToJavaRegex`:
* The first `]` in a bracket expression does not need to be escaped in Posix,translate to `\]`.
* Same as above for a negating bracket expression like `[^][]`, translate to `[^\]\[]`.
* Any `[` in a bracket expression does not need to be escaped in Posix, translate to `\[`.
* Any `]` not in a bracket expression is valid in both Posix and Java, no translation.
* A backslash before the closing bracket like `[.f\]` is not an escape of the closing bracket, the backslash needs to be escaped for Java, translate to `[.f\\]`.
* Do not perform the above translations within an escape via `\`.
* Do not perform the above translations for Posix "classes" like `[[:word:]]` or `[[:digit:]]` and their negation `[-[:word]]`.
* Do not perform the above translations for single-bracket Posix classes like `[:digit:]`, and handle the case of single-bracket Posix classes inside bracket expressions, like `[[:digit:]-.]`.

Test cases have been added.

There are however two regexes that still don't work, but those look invalid. To let jnano not trip over these, any `PatternSyntaxException` lets jnano just ignore the particular rule. A warning is logged in such cases.

Fixes jline#1156