[Crash-utility] crash-4.0.2.12 PPC64 changes to make it understand 64k pagesize

Hi Dave & Haren, Here are the changes I made to "crash" to function with PPC64 64k pagesize. Instead of adding whole set of indexs, shifts, masks, macros and new vtop() routines - I generalized 4-level pagetable support and set & compute indexes, shift and masks correctly for 4K and 64K. Tested with 4K pagesize and 64K pagesize kernels on PPC64. Please review. Thanks, Badari