* 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.
* _scm.h: if HAVE_RESTARTS is defined then don't use a SYSCALL
loop.
* posix.c (scm_uname): interpret only negative values as an error.
Solaris normally returns a positive value.
* script.c (scm_compile_shell_switches): if we are not going into
an interactive repl, set scm_mask_ints to zero so that asyncs can
run.
* simpos.c (scm_system): don't ignore/unignore signals around
the "system" call.
* posix.c (scm_open_pipe): don't ignore/unignore signals around
the "popen" call.
* init.c (scm_boot_guile_1): don't call scm_init_signals, it's
done in boot-9.scm instead.
* scmsigs.c, async.c: Major rewriting of signal handling code.
(scm_sigaction): new procedure.
(scm_sleep): don't wrap sleep in SCM_SYSCALL, it would mess up the
timing.
(scm_raise): return unspecified, throw error on failure.
* boot-9.scm: signal-handler, alarm-thunk: removed.
don't define ticks-interrupt etc.
top-repl: install signal handlers for SIGINT, SIGFPE, SIGSEGV, SIGBUS
during call to scm-style-repl.
* acconfig.h: mention HAVE_RESTARTS.
* configure.in: check for sigaction and restartable system calls.
