bug 304833 allow loading help: uris on non-mac systems

r=bsmedberg sr=roc

modules/libpref/src/init/all.js

@@ -458,7 +458,9 @@ pref("network.protocol-handler.external.data", false);
 pref("network.protocol-handler.external.ms-help", false);
 pref("network.protocol-handler.external.shell", false);
 pref("network.protocol-handler.external.vnd.ms.radio", false);
+#ifdef XP_MACOSX
 pref("network.protocol-handler.external.help", false);
+#endif
 pref("network.protocol-handler.external.disk", false);
 pref("network.protocol-handler.external.disks", false);
 pref("network.protocol-handler.external.afp", false);