* stime.h: prototype for scm_times.

* stime.h: prototype for scm_times.
* stime.c (scm_times): new procedure.
* ioext.c (scm_fseek): if the first argument is a file descriptor
call lseek.
(scm_ftell): if the first argument is a file descriptor call lseek
(sic).
* filesys.h: prototypes for scm_open_fdes, scm_fsync.
* filesys.c (scm_chmod): if the first argument is a file descriptor,
call fchmod.
(scm_chown): if the first argument is a port or file descriptor,
call fchown.
(scm_truncate_file): new procedure.
Add DEFER/ALLOW INTS to a few other procedures.
(scm_fsync): new procedure.
(scm_open_fdes): new procedure.
(scm_open): use scm_open_fdes.  If mode isn't specified, 666 will
now be used.
(scm_fcntl): the first argument can now be a file descriptor.  The
third argument is now optional.

* posix.c (scm_execl, scm_execlp): make the filename argument
compulsory, since omitting it causes SEGV.
(scm_sync): return unspecified instead of #f.
(scm_execle): new procedure.
(environ_list_to_c): new procedure.
(scm_environ): use environ_list_to_c.  disable interrupts.
(scm_convert_exec_args): take pos and subr arguments and
improve error checking.

* boot-9.scm: define tms accessors: clock, utime, stime, cutime,
cstime.