* syssignal.h: Don't #include <signal.h>

	* alloc.c: #include <signal.h>, but before "config.h".

src/alloc.c

@@ -17,6 +17,7 @@ You should have received a copy of the GNU General Public License
 along with GNU Emacs; see the file COPYING.  If not, write to
 the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  */
 
+#include <signal.h>
 
 #include "config.h"
 #include "lisp.h"

src/syssignal.h

@@ -19,7 +19,11 @@ the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  */
 
 #ifdef POSIX_SIGNALS
 
-#include <signal.h>
+/* Don't #include <signal.h>.  That header shouldalways be #included
+   before "config.h", because some configuration files (like s/hpux.h)
+   indicate that SIGIO doesn't work by #undef-ing SIGIO.  If this file
+   #includes <signal.h>, then that will re-#define SIGIO and confuse
+   things.  */
 
 #define SIGMASKTYPE sigset_t