Add benchmarks for wxImage methods.

Build a GUI version of the benchmark program too and use it to benchmark
wxImage loading methods for now (more will be added later).

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@74319 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

tests/benchmarks/bench.cpp

@@ -20,6 +20,10 @@
 #include "wx/cmdline.h"
 #include "wx/stopwatch.h"
 
+#if wxUSE_GUI
+    #include "wx/frame.h"
+#endif
+
 #include "bench.h"
 
 // ----------------------------------------------------------------------------