Vendor raptor source files (was embedded gitlink)

Tree vendored at upstream 0019c5dd; origin + license recorded in
raptor/VENDOR.txt. Windows SDL dev packages excluded via .gitignore.

raptor/src/shadow.h

@@ -0,0 +1,11 @@
+#pragma once
+
+extern int num_gshadows;
+extern int num_shadows;
+
+void SHADOW_Init(void);
+void SHADOW_MakeShades(void);
+void SHADOW_GAdd(int item, int x, int y);
+void SHADOW_Add(int item, int x, int y);
+void SHADOW_DisplayGround();
+void SHADOW_DisplaySky();