Changes to compile under gnu-win32, from Marcus Daniels:

Changes to compile under gnu-win32, from Marcus Daniels:
* stime.c (tzset): If tzset isn't provided, make it a NOP.
(scm_localtime): Change SCM_EOF to SCM_EOL.
(scm_mktime): Likewise.
* socket.c: Don't include sys/un.h unless autoconf tells
us Unix domain sockets are available.
(scm_fill_sockaddr): Ignore Unix domain code.
(scm_addr_vector): Likewise.
(scm_init_addr_buffer): Likewise.
(scm_socketpair): Don't include unless socketpair was
found during autoconf.
* simpos.c (SYSTNAME): Treat cygwin like Unix.
* scmsigs.c (scm_pause): Don't include unless pause was found
during autoconf.
* posix.c (scm_getgroups): Don't include unless support function
was found during autoconf (in this case, getgroups).
(scm_setpwent): For setpwent.
(scm_setegid): For setegid.
* net_db.c (scm_inet_netof): Don't include unless support
function was found during autoconf (in this case, inet_netof).
(scm_lnaof): For inet_lnaof.
(scm_inet_makeaddr): For inet_makeaddr.
(scm_getnet): For getnetent, getnetbyname, getnetbyaddr.
(scm_getproto): For getprotoent.
(scm_getserv): For getservent.
(scm_sethost): For sethostent, endhostent.
(scm_setnet): For setnetent, endnetent.
(scm_setproto): For setprotoent, endprotoent.
(scm_setserv): For setservent, endservent.
* scmconfig.h.in: Regenerated.