Visual Studio 2008 Projects: More Cleanups and Tweaks

Remove items from the projects that are no longer necessary to build
glibmm[1], and generate debug info (.pdb files, with little to no
performance defecit) for release builds as well.  These changes also fixes
the builds of glibmm and gtkmm as the glibmm_interface_implementation test
now runs successfully, and the gtkmm demo program now starts without
crashing (although it still does crash when a window is being closed).

	* MSVC_Net2008/*.vproj: Remove the build of blank.cpp and the /vd2
	  build options, as they are no longer needed.
	* MSVC_Net2008/giomm.vcproj:
	* MSVC_Net2008/glibmm.vcproj: Generate Debug Info for the Release
	  builds as well.