[MSan][MIPS] Fix for some failing tests on MIPS64

Enabling internal ptrace for mips, which fixes some
ptrace related tests. Along with this fixing some
other failures.

Reviewers: Reviewers: eugenis, kcc, samsonov

Subscribers: dsanders, sagar, lldb-commits

Differential Revision: http://reviews.llvm.org/D7332

llvm-svn: 229656