[ticket/12140] Remove the diff class / MOD text build script

PHPBB3-12140
Merge remote-tracking branch 'naderman/ticket/12140' into develop-olympus

* naderman/ticket/12140:
  [ticket/12140] Remove the diff class / MOD text build script
Merge branch 'develop-olympus' into develop

* develop-olympus:
  [ticket/12140] Remove the diff class / MOD text build script

Conflicts:
	build/build_diff.php