[NTOS]: Enable MmPageEntireDriver by implementing MiSetPagingOfDriver.

[NTOS]: Call MiEnablePagingOfDriver from MmLoadSystemImage and implement it. All the work is done other than actually enabling paging, which requires system working set support.
[NTOS]: Implement MiWriteProtectSystemImage and MiComputeDriverProtection. All the work is done other than actually setting the bits on the pages, since I wanted to avoid too many changes.
[NTOS]: MmCheckSystemImage returns STATUS_INVALID_IMAGE_PROTECT, not STATUS_INVALID_IMAGE_FORMAT, so the branch in MmLoadSystemImage needs to check for the correct status code.
[NTOS]: Support FLG_SHOW_LDR_SNAPS for the kernel loader.

svn path=/trunk/; revision=46977