Generate RPG data structure from result metadata

[janfh]

Feature to generate RPG data structure from column metadata.

Added statement qualifier "rpg". E.g:

rpg: select cast('' as varchar(100)) as my_text, current_timestamp as my_timestamp, cast(1.0 as numeric(13, 2)) as my_val from sysibm.sysdummy1;

generates:

**free

// statement: select cast('' as varchar(100)) as my_text, current_timestamp as my_timestamp, cast(1.0 as numeric(13, 2)) as my_val from sysibm.sysdummy1

// Row data structure
dcl-ds row_t qualified template;
  my_text varchar(100);
  my_timestamp timestamp;
  my_val zoned(13 : 2);
end-ds;

[worksofliam]

I left a comment about moving logic to another function.

I don't want the logic to generate the content in this function really. We should move it elsewhere so we can write test cases for it.

Please make this change and then lmk when to look again.

[worksofliam]

Left another review.

[janfh]

@worksofliam : Where do you want the tests? A new testsuite? Please continue to comment if you want me to change something else :) I will continue working on this tomorrow

[worksofliam]

@janfh For my own sake of mind, I have had to move this to fix day 2 (Wednesday 23rd) and this will be the first PR I look at then. I may get to it over the weekend if I find a moment. Thanks for your work here!

Also, let's chat on chat.ibmioss.org sometime.