IPC-server hardening and update

- add IMPLEMENT_RANDOMIZE_STACK for ipcThread()
- log / print boost interprocess exceptions
- use MAX_URI_LENGTH in guiconstants.h (also used in qrcodedialog.cpp)
- remove unneeded includes and ipcShutdown() from qtipcserver.cpp
- fix a small mem-leak by deleting mq before re-using it
- make ipcThread() and ipcThread2() static functions
- add some more comments

src/qt/qtipcserver.h

@@ -1,4 +1,9 @@
+#ifndef QTIPCSERVER_H
+#define QTIPCSERVER_H
+
+// Define Bitcoin-Qt message queue name
 #define BITCOINURI_QUEUE_NAME "BitcoinURI"
 
 void ipcInit();
-void ipcShutdown();
+
+#endif // QTIPCSERVER_H