[NTOS/MM]

[NTOS/MM]
Miscellaneous fixes for legacy Mm section implementation
 - Always allocate a private page for IMAGE_SCN_CNT_UNINITIALIZED_DATA
 - Make sure a shared page is present before writing on a COW mapping and making a private copy.
 - Fix a race condition : when paging out a file section, old Mm lists all of the process maps, removing them one after the other and lowering the page reference count in the process. Sometimes a page fault occur in the process, the mapping is added, but the page refcount is not bumped because it requires locking the corresponding segment. Manage page refcount under segment lock.
CORE-12047

svn path=/trunk/; revision=72989