[NTOS]: Remove many hacks in freelist.c regarding the differences between PHYSICAL_PA...

[NTOS]: Remove many hacks in freelist.c regarding the differences between PHYSICAL_PAGE and MMPFN. ReferenceCount field is now accessed directly. LockCount is gone. Type is gone: if a page is used, it has a consumer and is in the ActiveAndValid state, if it's free, it's on the free or zero page list. Get rid of Zero, if a page is zeroed, it is on the zero page list.
[NTOS]: These changes will allow a smoother migration to MMPFN later on.

svn path=/trunk/; revision=45577