This commit does a number of things:
- remove some dead wchar configury from configure.ac and gdkconfig.h
- repurpose gdkconfig.h as header that contains GDK_WINDOWING_foo
macros for each included backend, include it in gdk.h and install
it in $includedir instead of below $libdir
- drop the backend from the library names
- build libgdk-3.0.la as a convenience lib and include it in libgtk-3.0.la
It does not yet enable building multiple backends at the same time.
We build the examples that are included in the 'getting started'
chapter of the docs to prevent them from bitrotting. Also
remove the awk scripts used to extract the old examples from
the tutorial, since the tutorial is gone. I'm still leaving
the examples themeselves in place, for possible inclusion in
'getting started' later on.
