Leading tilda for prefix operator lambdas should only be used when the operator can also be a infix operator

```
e.g. the following is wrong:

> decompile <@ (~~~) @>;;
val it : string = "(~~~~)"

it should obviously decompile to simply (~~~)
```

Original issue reported on code.google.com by `stephen....@gmail.com` on 23 Apr 2012 at 2:21
