More Visual C++ 2010 adjustments and hacks.
**/Makefile.kmk: Cosmetic changes.
NOINST -> INSTTYPE=none; adding DEBUG_INSTTYPE=both if the NOINST was because of code signing. This will make the .PDBs be installed into stage/debug/ for signed drivers (i.e. with .INF files).
add/w/InstallHelper/Makefile.kmk: Drop the template, only build on x86 for now because of WINPSDK.
Windows Guest Additions: Added own NSIS plugin VBoxInstallHelper.