Working template (RmlUi 6.2)

Needs:
- Lua plugin
- SVG plugin

vendor/rmlui_backend/RmlUi_Include_Xlib.h

@@ -0,0 +1,18 @@
+#pragma once
+
+#ifndef RMLUI_DISABLE_INCLUDE_XLIB
+
+	#include <X11/Xlib.h>
+
+	// The None and Always defines from X.h conflicts with RmlUi code base,
+	// use their underlying constants where necessary.
+	#ifdef None
+		// Value 0L
+		#undef None
+	#endif
+	#ifdef Always
+		// Value 2
+		#undef Always
+	#endif
+
+#endif