Add support for Controller Keys, inspired by similar code by CtrlAltStudio Viewer

Dear Alpha Users who are curious about this:
A = Alt
B = Shift
X = Ctrl
Y = Escape
Back = Toggle Flycam mode (Use this, it's fun!!!)
Start = Toggle Cursor mode
Right Stick Click = Toggle Mouselook
Left Stick Click = Jump/Fly

Enjoy, I know I do!

indra/llwindow/llkeyboard.h

@@ -113,6 +113,12 @@ public:
 	F32				getKeyElapsedTime( KEY key );  // Returns time in seconds since key was pressed.
 	S32				getKeyElapsedFrameCount( KEY key );  // Returns time in frames since key was pressed.
 
+	void setControllerKey(KEY key, bool level)
+	{
+		mControllerKeys[key] = mKeyLevel[key] = level;
+		(level ? mKeyDown[key] : mKeyUp[key]) = true;
+	}
+
 protected:
 	void 			addKeyName(KEY key, const std::string& name);
 
@@ -127,6 +133,7 @@ protected:
 	BOOL			mKeyRepeated[KEY_COUNT];	// Key was repeated
 	BOOL			mKeyUp[KEY_COUNT];			// Up edge
 	BOOL			mKeyDown[KEY_COUNT];		// Down edge
+	BOOL			mControllerKeys[KEY_COUNT];	// Keys held in controller
 	KEY				mCurTranslatedKey;
 	KEY				mCurScanKey;		// Used during the scanKeyboard()