update mac gui to recognize global pex

macosx/PrefsController.m

@@ -81,6 +81,9 @@
         //set peer connection values
         tr_setGlobalPeerLimit(fHandle, [fDefaults integerForKey: @"PeersGlobal"]);
         
+        //set pex
+        [self setPEX: nil];
+        
         //set encryption
         [self setEncryptionMode: nil];
         
@@ -340,6 +343,11 @@
     [fDefaults setInteger: count forKey: @"PeersTorrent"];
 }
 
+- (void) setPEX: (id) sender
+{
+    tr_setPexEnabled(fHandle, [fDefaults boolForKey: @"PEXGlobal"]);
+}
+
 - (void) setEncryptionMode: (id) sender
 {
     tr_setEncryptionMode(fHandle, [fDefaults boolForKey: @"EncryptionPrefer"] ?