[perl #113980] pp_syscall: "I32 retval" truncates the returned value

I noticed today that syscall(9, ...) (mmap) doesn't work for me.

The problem is obvious, pp_syscall() uses I32 for retval and the
"long" address doesn't fit into "int".

The one-liner below should fix the problem.

pp_sys.c

@@ -5456,7 +5456,7 @@ PP(pp_syscall)
     register I32 items = SP - MARK;
     unsigned long a[20];
     register I32 i = 0;
-    I32 retval = -1;
+    IV retval = -1;
 
     if (PL_tainting) {
 	while (++MARK <= SP) {