SCM_THREAD_CRITICAL_SECTION_START/END unless USE_THREADS is defined.
* ports.h: prototypes too.
* ports.c (scm_mode_bits, scm_port_mode): moved from fports.c.
* fports.h: prototype too.
* fports.c (scm_evict_ports): moved from ioext.c.
* ports.c (scm_close_port): return a boolean instead of unspecified.
throw an error if an error other than EBADF occurs.
* filesys.h: scm_close prototype.
* filesys.c (scm_close): new procedure, can close file descriptors
and ports (scsh compatible).
* ports.c (scm_flush_all_ports): SCM_PROC incorrectly allowed an
optional argument.
* _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.
