ada: Fix Ada bootstrap on macOS

ada: Fix Ada bootstrap on macOS

The recent warning changes broke Ada bootstrap on macOS:

adaint.c: In function '__gnat_copy_attribs':
adaint.c:3336:10: error: implicit declaration of function 'utimes'; did you
mean 'utime'? [-Wimplicit-function-declaration]
 3336 |      if (utimes (to, tbuf) == -1) {
      |          ^~~~~~
      |          utime
adaint.c: In function '__gnat_kill':
adaint.c:3597:3: error: implicit declaration of function 'kill'
[-Wimplicit-function-declaration]
 3597 |   kill (pid, sig);
      |   ^~~~
terminals.c: In function 'allocate_pty_desc':
terminals.c:1196:12: error: implicit declaration of function 'openpty'; did
you mean 'openat'? [-Wimplicit-function-declaration]
 1196 |   status = openpty (&master_fd, &slave_fd, NULL, NULL, NULL);
      |            ^~~~~~~
      |            openat
terminals.c: In function '__gnat_setup_winsize':
terminals.c:1392:6: error: implicit declaration of function 'kill'
[-Wimplicit-function-declaration]
 1392 |      kill (desc->child_pid, SIGWINCH);
      |      ^~~~

This patch fixes this by including the necessary headers: <sys/time.h>
for utimes, <signal.h> for kill, and <util.h> for openpty.  With those
changes, the build completed on x86_64-apple-darwin2[0-3] (make check
still running).

2023-12-01  Rainer Orth  <ro@CeBiTec.Uni-Bielefeld.DE>

	gcc/ada:
	* adaint.c [__APPLE__]: Include <signal.h>, <sys/time.h>.
	* terminals.c [!_WIN32]: Include <signal.h>.
	[__APPLE__]: Include <util.h>.
	Fix typos.