Remove useless "if" tests before free. Deprecate "free" module. * doc/posix-functions/free.texi: Mention that this module is no longer useful. * modules/free (Notice): Say this module is obsolete. * modules/readutmp (Depends-on): Remove free. * lib/save-cwd.c (free_cwd): Remove useless "if" before free. * lib/putenv.c (putenv): Likewise. * lib/gc-gnulib.c (gc_cipher_close): Likewise. * lib/getaddrinfo.c (freeaddrinfo): Likewise. * tests/test-c-strcasestr.c (main): Likewise. * tests/test-c-strstr.c (main): Likewise. * tests/test-mbscasestr1.c (main): Likewise. * tests/test-mbscasestr2.c (main): Likewise. * tests/test-mbsstr1.c (main): Likewise. * tests/test-mbsstr2.c (main): Likewise. * tests/test-memmem.c (main): Likewise. * tests/test-strcasestr.c (main): Likewise. * tests/test-striconv.c (main): Likewise. * tests/test-striconveh.c (main): Likewise. * tests/test-striconveha.c (main): Likewise. * tests/test-strstr.c (main): Likewise.