Avoid missing-declarations warning in various tests. * tests/test-argp.c (fail, test1, test2, test_file, test3, test4, test5, test6, test_optional, test7, test8, test9, test10, test11, test12, test13, test14, test15, test_fun): Declare static. * tests/test-cnd.c (test_cnd_wait): Likewise. * tests/test-cond.c (test_cond): Likewise.