Fix hotkey debug spew

Two issues:

* Unassigned hotkeys were being passed to WX in the menu strings as
  "<unassigned>". WX doesn't recognise this, and prints debug each time.
  Unassigned hotkeys are no longer rare or naughty, so we shouldn't provoke
  debug spew. Suppress by not appending hotkey strings for actions with 0
  (i.e. unassigned) hotkey IDs.
* The zone cutout tool uses GR_KB_SHIFT, not MD_SHIFT. This causes
  "unknown hotkey" spew from WX.

common/hotkeys_basic.cpp

@@ -198,13 +198,22 @@ wxString AddHotkeyName( const wxString& aText, int aHotKey, HOTKEY_ACTION_TYPE a
         switch( aStyle )
         {
         case IS_HOTKEY:
-            msg << wxT( "\t" ) << keyname;
+        {
+            // Don't add a suffix for unassigned hotkeys:
+            // WX spews debug from wxAcceleratorEntry::ParseAccel if it doesn't
+            // recognise the keyname, which is the case for <unassigned>.
+            if( aHotKey != 0 )
+            {
+                msg << wxT( "\t" ) << keyname;
+            }
             break;
-
+        }
         case IS_COMMENT:
+        {
             msg << wxT( " (" ) << keyname << wxT( ")" );
             break;
         }
+        }
     }
 
 #ifdef USING_MAC_CMD

pcbnew/tools/drawing_tool.cpp

@@ -125,7 +125,7 @@ TOOL_ACTION PCB_ACTIONS::drawZoneKeepout( "pcbnew.InteractiveDrawing.keepout",
 
 TOOL_ACTION PCB_ACTIONS::drawZoneCutout( "pcbnew.InteractiveDrawing.zoneCutout",
         AS_GLOBAL, 
-        GR_KB_SHIFT + 'C', LEGACY_HK_NAME( "Add a Zone Cutout" ),
+        MD_SHIFT + 'C', LEGACY_HK_NAME( "Add a Zone Cutout" ),
         _( "Add a Zone Cutout" ), _( "Add a cutout area of an existing zone" ),
         add_zone_cutout_xpm, AF_ACTIVATE );