kBuild 2751 -> 2763: Fixed VBoxDrv.pdb install location. New shot at the ENOSPC issue. Reduced memory usage by ~20MB (only applicable to windows, other needs new binaries built first). Fixed occational crash on 64-bit windows when using Ctrl-C or Ctrl-Break to abort the build. Optimized bits of subheader/subfooter.kmk that was done 160000 times while loading the Makefiles for the VBox source tree.
