Added plugin support for drawing messages to screen.

- Either a single string will be drawn to screen, or nothing will be drawn.
 - Intelligently registers and unregisters drawing callback to minimize overhead when no message is being displayed.
 - Currently does not support newline characters (\r or \n). Newlines will cause text to be drawn overlapped.

xpcPlugin/xpcDrawing.h

@@ -0,0 +1,8 @@
+#ifndef xpcDrawing_h
+#define xpcDrawing_h
+
+void XPCClearMessage();
+
+void XPCSetMessage(int x, int y, char* msg);
+
+#endif