AI 149496: Backport emulator-related donut fixes into cupcake.

This includes the following fixes:
  - remove potential qemud crash at system boot
  - fix GPS fix emulation
  - fix inter-emulator networking (DNS resolution helper now behaves correctly on all IPv6-capable systems)
  - add -prop <name>=<value> option to add system properties on boot
  - allow F5 keybinding for SEARCH on keyboard-less hardware configurations
  - allow skins to provide a "search" button
  - fixed bad QADD/QSUB/QDADD/QDSUB ARM CPU instructions emulation

Automated import of CL 149496

emulator/qemud/qemud.c

@@ -849,6 +849,10 @@ fdhandler_close( FDHandler*  f )
 static void
 fdhandler_shutdown( FDHandler*  f )
 {
+    /* prevent later fdhandler_close() to
+     * call the receiver's close.
+     */
+    f->receiver->close = NULL;
 
     if (f->out_first != NULL && !f->closing)
     {
@@ -856,9 +860,6 @@ fdhandler_shutdown( FDHandler*  f )
         f->closing = 1;
         fdhandler_remove(f);
         fdhandler_prepend(f, &f->list->closing);
-
-        /* notify the receiver that we're closing */
-        receiver_close(f->receiver);
         return;
     }