Fix building with GHC 7.6.1

This change doesn't have WXWIDGETS_2_8 specific change for helping
to pick (or merge) this change to HEAD.

I'll commit WXWIDGETS_2_8 specific change next time.
Fix building wx-2.8 with GHC 7.6.x

This is wx-2.8 specific change to fix building with GHC 7.6.x.
Bump wxdirect version number to 0.13.1.3
Merge pull request #11 from shelarcy/WXWIDGETS_2_8

Fix building WXWIDGETS_2_8 with GHC 7.6.1