Update Checkref.pl

[Stan]

The scripts that checks all the reference of all files to find unused stuff is currently broken somewhat.

It'd be nice to update it. It should take into account variants, also, it should not break for Json.

[elexis]

somewhat should be specified. I guess you already noticed the ticket on the a23 milestone.

[Stan]

Ah so yeah, that's part of it.

Variants are not taken into account leading to false positives in the script. Biomes are not taken into account #4777

Random maps trigger errors

Loading random maps...
Use of uninitialized value in concatenation (.) or string at checkrefs.pl line 444.
Use of uninitialized value in concatenation (.) or string at checkrefs.pl line 444.
Use of uninitialized value in concatenation (.) or string at checkrefs.pl line 444.
Use of uninitialized value in concatenation (.) or string at checkrefs.pl line 444.
Use of uninitialized value in concatenation (.) or string at checkrefs.pl line 444.
Use of uninitialized value in concatenation (.) or string at checkrefs.pl line 444.
Use of uninitialized value in concatenation (.) or string at checkrefs.pl line 444.
Use of uninitialized value in concatenation (.) or string at checkrefs.pl line 444.
Use of uninitialized value in concatenation (.) or string at checkrefs.pl line 444.
Use of uninitialized value in concatenation (.) or string at checkrefs.pl line 444.
Use of uninitialized value in concatenation (.) or string at checkrefs.pl line 444.
Use of uninitialized value in concatenation (.) or string at checkrefs.pl line 444.

and GUI too

Loading GUI XML...
Can't stat ../../../binaries/data/mods/public/gui/modmod: No such file or directory
 at checkrefs.pl line 50.

[Stan]

This patch makes variant part of the script.

[Stan]

Fixed in r22096

Improve and fix checkrefs.pl, add a readme for usage, add mod support, add command line arguments. Reviewed by: @Itms Comments by: @elexis

Differential Revision: ​​https://code.wildfiregames.com/D1381