Enable breakpoints and read/write GPRs for ppc64le

Add support for ppc64le to create breakpoints and read/write
general purpose registers.
Other features for ppc64le and functions to read/write
other registers are being implemented.

Patch by Alexandre Yukio Yamashita (alexandreyy)
Differential Revision: https://reviews.llvm.org/D38323

llvm-svn: 315008