tests: avoid some compiler warnings

tests: avoid some compiler warnings

Mostly Simon's modules; warnings reported by gcc 4.3.4 on coreutils.

* tests/test-getaddrinfo.c (simple): Mark static, and allow string
literals.
* tests/test-memchr.c (main): Avoid type mismatch.
* tests/test-arpa_inet.c (main): Avoid unused parameters.
* tests/test-base64.c (main): Likewise.
* tests/test-getdelim.c (main): Likewise.
* tests/test-gethostname.c (main): Likewise.
* tests/test-getline.c (main): Likewise.
* tests/test-netinet_in.c (main): Likewise.
* tests/test-select.c (open_server_socket, main): Likewise.
* tests/test-select-stdin.c (main): Likewise.
* tests/test-sockets.c (main): Likewise.
* tests/test-strsignal.c (main): Likewise.
* tests/test-sys_select.c (main): Likewise.
* tests/test-sys_socket.c (main): Likewise.
* tests/test-u64.c (main): Likewise.
* tests/test-xfprintf-posix.c (main): Likewise.
* tests/test-xvasprintf.c (test_xvasprintf, main): Likewise.

Signed-off-by: Eric Blake <ebb9@byu.net>