[asan] Print SHADOW_SCALE and SHADOW_GRANULARITY as decimal values.

Summary:
During the review of http://reviews.llvm.org/D9199 where I had originally
changed the debug_mapping.cc test to accept hexadecimal values, we realized
that SHADOW_SCALE and SHADOW_GRANULARITY ought to be printed as decimal values.
This patch makes that change.

This patch also adds a '0x' prefix to the SHADOW_OFFSET to make it clear that
it is hexadecimal while the other two are decimal.

Reviewers: kcc, timurrrr, samsonov

Reviewed By: timurrrr, samsonov

Subscribers: samsonov, llvm-commits, sagar

Differential Revision: http://reviews.llvm.org/D9224

llvm-svn: 235798