Add support for ARM and ARM64 breakpad generated minidump files (version 2).

In this patch I add support for ARM and ARM64 break pad files. There are two flavors of ARM: Apple where FP is R7, and non Apple where FP is R11. Added minimal tests that load up ARM64 and the two flavors or ARM core files with a single thread and known register values in each register. Each register is checked for the exact value.

This is a fixed version of: https://reviews.llvm.org/D49750

The changes from D49750 are:

Don't init the m_arch in the Initialize call as a system info isn't required. This keeps the thread list, module list and other tests from failing
Added -Wextended-offsetof to Xcode project so we catch use extended usages of offsetof before submission
Fixed any extended offset of warnings

Differential Revision: https://reviews.llvm.org/D50336

llvm-svn: 339032