add SDL2 sources

thirdparty/SDL2-src/TODO.txt

@@ -0,0 +1,10 @@
+Future work roadmap:
+ * http://wiki.libsdl.org/moin.cgi/Roadmap
+
+ * Check 1.2 revisions:
+	3554 - Need to resolve semantics for locking keys on different platforms
+	4874 - Do we want screen rotation?  At what level?
+	4974 - Windows file code needs to convert UTF-8 to Unicode, but we don't need to tap dance for Windows 95/98
+	4865 - See if this is still needed (mouse coordinate clamping)
+	4866 - See if this is still needed (blocking window repositioning)
+