add SDL2 sources

thirdparty/SDL2-src/test/autogen.sh

@@ -0,0 +1,12 @@
+#!/bin/sh
+#
+# Regenerate configuration files
+cp acinclude.m4 aclocal.m4
+found=false
+for autoconf in autoconf autoconf259 autoconf-2.59
+do if which $autoconf >/dev/null 2>&1; then $autoconf && found=true; break; fi
+done
+if test x$found = xfalse; then
+    echo "Couldn't find autoconf, aborting"
+    exit 1
+fi