Always return 64-bit 0 in response to a message to nil on x86.

objc_msgSend.x86-32.S

@@ -60,6 +60,8 @@
 	fldz
 .else 
 	xor   %eax, %eax                     # return 0 (int)
+	xor   %edx, %edx                     # Return 64-bit zero (%edx is
+	                                     # caller-save, so it's safe to do this in the general case.
 .endif
 	ret
 5:                                       # slowSend:

sendmsg2.c

@@ -9,7 +9,7 @@
 
 void objc_send_initialize(id object);
 
-static id nil_method(id self, SEL _cmd) { return nil; }
+static long long nil_method(id self, SEL _cmd) { return 0; }
 
 static struct objc_slot nil_slot = { Nil, Nil, 0, 1, (IMP)nil_method };