tests: Fix a few compilation errors on Solaris 11 OmniOS with gcc 14. * tests/test-accept.c: Omit the signature check on Solaris. * tests/test-gethostname.c: Likewise. * tests/test-getpeername.c: Likewise. * tests/test-getsockname.c: Likewise. * tests/test-getsockopt.c: Likewise. * tests/test-recvfrom.c: Likewise. * doc/posix-functions/accept.texi: Mention the Solaris 11 OmniOS problem. * doc/posix-functions/gethostname.texi: Likewise. * doc/posix-functions/getpeername.texi: Likewise. * doc/posix-functions/getsockname.texi: Likewise. * doc/posix-functions/getsockopt.texi: Likewise. * doc/posix-functions/recvfrom.texi: Likewise.