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/include/SDL2-devel-2.28.2-mingw/SDL2-2.28.2/test/COPYING

@@ -0,0 +1,8 @@
+
+The test programs in this directory tree are for demonstrating and
+testing the functionality of the SDL library, and are placed in the
+public domain.
+
+October 28, 1997
+--
+	Sam Lantinga				(slouken@libsdl.org)