tests: Don't depend on the exact locale name. * tests/test-c-ctype.c: Include <stdlib.h>. (main): Test the return value of setlocale(). Try not only de_DE, but also de_DE.ISO-8859-1. * tests/test-vasnprintf-posix3.c (main): Try not only fa_IR.UTF-8, but also fa_IR. * tests/test-vasnwprintf-posix3.c (main): Likewise.