[scudo] ARM32 support

Summary:
With the previous modifications, the code works on ARM32. The random shuffle
test is unsupported on 32-bit platforms for the moment and being marked as
such. There is no hardware support for the checksum computation yet, this will
come at a later point.

Reviewers: kcc, alekseyshl

Subscribers: llvm-commits, aemerson, rengolin, mgorny

Differential Revision: https://reviews.llvm.org/D27957

llvm-svn: 290201