Include config.h first so that _GDK_EXTERN may be defined once
and only once during the build, so that we do not get warnings/
errors for macro redefinition.
https://bugzilla.gnome.org/show_bug.cgi?id=701251
There are sure regressions but basic stuff seems to be working
again after all the API breakage done with comments like
"Win32 and Quartz need to be ported still."
