tests: fold xglimage.{cpp,h} into xglrenderframework.{cpp,h}

XglImage is a part of the render framework.
diff --git a/tests/xgltestframework.cpp b/tests/xgltestframework.cpp
index a10c4cf..5b3b8c2 100644
--- a/tests/xgltestframework.cpp
+++ b/tests/xgltestframework.cpp
@@ -21,6 +21,7 @@
 //  DEALINGS IN THE SOFTWARE.
 
 #include "xgltestframework.h"
+#include "xglrenderframework.h"
 #include "GL/freeglut_std.h"
 //#include "ShaderLang.h"
 #include "GlslangToBil.h"