build: Check -lsocket -lnsl for Solaris.
* configure.ac: Check inet_addr for -lnsl, and socket for -lsocket.
Once I used LIB_SOCKET_NSL for the variable name, but it is already
used by AX_LIB_SOCKET_NSL in autoconf-archive as an alias of the
macro. So, I changed the variable name.
- GnuPG-bug-id: T3869
- Signed-off-by: NIIBE Yutaka <firstname.lastname@example.org>