Fix Qt build on OSX

Compiling boost::interprocess::message_queue against
boost 1.50 macports with -arch i386 (how releases are built,
for minimum download size and maximum compatibility) is failing:

src/qt/qtipcserver.cpp:37: error: no matching function for call to ‘boost::interprocess::message_queue_t<boost::interprocess::offset_ptr<void, int, long unsigned int, 0u> >::timed_receive(char (*)[257], long unsigned int, size_t&, unsigned int&, boost::posix_time::ptime&)’

This is probably a boost or macports bug, but since interprocess::message_queue
is only used for URI support, which isn't implemented on OSX anyway, I fixed
the build by #ifdef'ing out that code.

src/qt/qtipcserver.cpp

@@ -20,6 +20,14 @@ using namespace boost::posix_time;
 using namespace boost;
 using namespace std;
 
+#ifdef MAC_OSX
+// URI handling not implemented on OSX yet
+
+void ipcInit() { }
+void ipcShutdown() { }
+
+#else
+
 void ipcShutdown()
 {
     message_queue::remove(BITCOINURI_QUEUE_NAME);
@@ -50,11 +58,6 @@ void ipcThread(void* parg)
 
 void ipcInit()
 {
-#ifdef MAC_OSX
-    // TODO: implement bitcoin: URI handling the Mac Way
-    return;
-#endif
-
     message_queue* mq;
     char strBuf[257];
     size_t nSize;
@@ -86,3 +89,5 @@ void ipcInit()
         delete mq;
     }
 }
+
+#endif