Various cleanup in i18n code (having funcs implemented in two different places is tricky, you quickly forget to add/edit one, we already have this problem with ugly bplayer stub... e.g. since r53938, BLF_locale_explode was not implemented in non-WITH_INTERNATIONAL builds). Also tried to simplify #ifdef's here...

git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@53945 954f8c5b-7b00-dc11-b283-0030488c597c