XFree86: Input: Save/restore errno around SIGIO (bug #10683)

Make sure errno is saved and restored from the SIGIO handler, so errors
from system calls in input handlers don't break the interrupted code.
(cherry picked from commit 41c3069f7c)

hw/xfree86/common/xf86Events.c

@@ -510,12 +510,14 @@ static void
 xf86SigioReadInput(int fd,
 		   void *closure)
 {
+    int errno_save = errno;
     int sigstate = xf86BlockSIGIO();
     InputInfoPtr pInfo = (InputInfoPtr) closure;
 
     pInfo->read_input(pInfo);
 
     xf86UnblockSIGIO(sigstate);
+    errno = errno_save;
 }
 
 /*