Initial FreeBSD mips64 ProcessMonitor support

Committing early to ease tracking other ongoing POSIX changes.

Review: http://llvm-reviews.chandlerc.com/D1886


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@192387 91177308-0d34-0410-b5e6-96231b3b80d8