Update Visual Studio Property Sheets

-For the binary "installation", look for the DLL files with their file
 names consistent with the ones that are generated with the respective
 Visual Studio projects.
-Remove any stray GDK DLLs that were left over from a Broadway-enabled
 GDK when building a non-Broadway-enabled GTK+ binary set.
Clean up Property Sheets a bit

...from the last commit, as some unecessary stuff was left over in the
Visual Studio 2010 property sheets.
gtksearchentry: Provide an accessible name

https://bugzilla.gnome.org/show_bug.cgi?id=706014