[PowerPC][asan] Update asan to handle changed memory layouts in newer kernels

In more recent Linux kernels with 47 bit VMAs the layout of virtual memory
for powerpc64 changed causing the address sanitizer to not work properly. This
patch adds support for 47 bit VMA kernels for powerpc64 and fixes up test
cases.

https://reviews.llvm.org/D40908

There is an associated patch for trunk.

Tested on several 4.x and 3.x kernel releases.

llvm-svn: 320110