Don't use <sys/signal.h>

This legacy header appears to be unused. Removing its includes
avoids numerous warnings when compiling with musl libc:

/usr/include/sys/signal.h:1:2: warning: #warning redirecting incorrect #include <sys/signal.h> to <signal.h> [-Wcpp]

configure.ac

@@ -198,7 +198,6 @@ AC_CHECK_HEADERS(sys/fmutex.h)
 AC_CHECK_HEADERS(sys/ioctl.h sys/sockio.h)
 AC_CHECK_HEADERS(sys/resource.h)
 AC_CHECK_HEADERS(sys/select.h)
-AC_CHECK_HEADERS(sys/signal.h)
 AC_CHECK_HEADERS(sys/socket.h)
 AC_CHECK_HEADERS(sys/time.h)
 AC_CHECK_HEADERS(sys/utsname.h)

src/main/select.c

@@ -7,9 +7,6 @@
 #include <errno.h>
 #include <signal.h>
 #include <string.h> /* FreeBSD FD_ZERO() macro calls bzero() */
-#ifdef HAVE_SYS_SIGNAL_H
-#include <sys/signal.h>
-#endif
 #ifdef __GNU__ /* For GNU Hurd bug workaround in set_handlers() */
 #include <sys/stat.h> /* OS/2 needs this after sys/types.h */
 #endif

src/osdep/generic.h

@@ -7,18 +7,10 @@
 #include <limits.h> /* may contain PIPE_BUF definition on some systems */
 #endif
 
-#ifdef HAVE_SYS_SIGNAL_H
-#include <sys/signal.h> /* may contain SA_RESTART */
-#endif
-
 #ifdef HAVE_STDDEF_H
 #include <stddef.h> /* may contain offsetof() */
 #endif
 
-#ifndef SA_RESTART
-#define SA_RESTART	0
-#endif
-
 #ifndef PIPE_BUF
 #define PIPE_BUF	512 /* POSIX says that. -- Mikulas */
 #endif

src/osdep/osdep.c

@@ -15,9 +15,6 @@
 #ifdef HAVE_SYS_IOCTL_H
 #include <sys/ioctl.h>
 #endif
-#ifdef HAVE_SYS_SIGNAL_H
-#include <sys/signal.h>
-#endif
 #include <sys/types.h>
 #ifdef HAVE_SYS_SOCKET_H
 #include <sys/socket.h>	/* Need to be after sys/types.h */

src/osdep/signals.c

@@ -8,9 +8,6 @@
 #include <signal.h>
 #include <stdlib.h>
 #include <string.h>
-#ifdef HAVE_SYS_SIGNAL_H
-#include <sys/signal.h>
-#endif
 #include <sys/types.h>
 #ifdef HAVE_SYS_WAIT_H
 #include <sys/wait.h>

src/viewer/dump/dump.c

@@ -8,9 +8,6 @@
 #include <stdio.h>
 #include <string.h>
 #include <sys/types.h> /* NetBSD flavour */
-#ifdef HAVE_SYS_SIGNAL_H
-#include <sys/signal.h>
-#endif
 #ifdef HAVE_FCNTL_H
 #include <fcntl.h> /* OS/2 needs this after sys/types.h */
 #endif