[NTOSKRNL]

[NTOSKRNL]
- Add MM_HAL_VA_END and use it in MiAddHalIoMappings instead of making assumptions about the page tables
- Add MM_SHARED_USER_DATA_VA for x86
- use MM_SHARED_USER_DATA_VA in Mm to avoid ambiguities
- fix or comment out USER_SHARED_DATA in asm headers, as it should be the kernel mode address here
- set Teb->ExceptionList to NULL on amd64, it is used as a link to the Wow64 TEB, if any

svn path=/trunk/; revision=55445