Overhaul the Visual Studio 2008 Projects

Give the Visual Studio 2008 Projects an overhaul, and clean them up in the
process by consolidating commonly-used items in property sheets, so to ease
future maintenance.

	* MSVC_Net2008/pangomm-build-defines.vsprops:
	* MSVC_Net2008/pangomm-version-paths.vsprops: Add property sheets
	  to group together commonly-used items so that the projects can
	  refer to them, so to ease future maintenance.
	* MSVC_Net2008/pangomm/pangomm.vcproj:
	* MSVC_Net2008/gendef/gendef.vcproj: Move to MSVC_Net2008/ and
	  clean up using the property sheets, and update the file paths
	  accordingly.  Stop building blank.cpp, as the IDE recognize the
	  .cc sources, and stop using the /vd2 option, as it is a source
	  of weird crashes.
	* MSVC_Net2008/pangomm.sln:
	  MSVC_Net2008/filelist.am: Update file paths accordingly.