maint: remove unused include for signal.h

A number of files were including signal.h but not using any
of the functions it provides

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

bsd-user/signal.c

@@ -21,7 +21,6 @@
 #include <string.h>
 #include <stdarg.h>
 #include <unistd.h>
-#include <signal.h>
 #include <errno.h>
 
 #include "qemu.h"

hw/block/xen_disk.c

@@ -24,7 +24,6 @@
 #include <stdarg.h>
 #include <string.h>
 #include <unistd.h>
-#include <signal.h>
 #include <inttypes.h>
 #include <time.h>
 #include <fcntl.h>

hw/net/xen_nic.c

@@ -24,7 +24,6 @@
 #include <stdarg.h>
 #include <string.h>
 #include <unistd.h>
-#include <signal.h>
 #include <inttypes.h>
 #include <fcntl.h>
 #include <errno.h>

hw/usb/redirect.c

@@ -34,7 +34,6 @@
 #include "sysemu/char.h"
 
 #include <sys/ioctl.h>
-#include <signal.h>
 #include <usbredirparser.h>
 #include <usbredirfilter.h>
 

os-win32.c

@@ -26,7 +26,6 @@
 #include <mmsystem.h>
 #include <unistd.h>
 #include <fcntl.h>
-#include <signal.h>
 #include <time.h>
 #include <errno.h>
 #include <sys/time.h>

target-i386/translate.c

@@ -21,7 +21,6 @@
 #include <stdio.h>
 #include <string.h>
 #include <inttypes.h>
-#include <signal.h>
 
 #include "qemu/host-utils.h"
 #include "cpu.h"

target-mips/helper.c

@@ -21,7 +21,6 @@
 #include <stdio.h>
 #include <string.h>
 #include <inttypes.h>
-#include <signal.h>
 
 #include "cpu.h"
 #include "sysemu/kvm.h"

target-sh4/helper.c

@@ -21,7 +21,6 @@
 #include <stdio.h>
 #include <string.h>
 #include <inttypes.h>
-#include <signal.h>
 
 #include "cpu.h"
 

target-tricore/helper.c

@@ -20,7 +20,6 @@
 #include <stdio.h>
 #include <string.h>
 #include <inttypes.h>
-#include <signal.h>
 
 #include "cpu.h"
 

tests/tcg/testthread.c

@@ -2,7 +2,6 @@
 #include <stdlib.h>
 #include <stdio.h>
 #include <string.h>
-#include <signal.h>
 #include <unistd.h>
 #include <inttypes.h>
 #include <pthread.h>