Resubmit rL345008 "Split MachinePipeliner code into header and cpp files"

The commit caused unclear failures in http://green.lab.llvm.org/green//job/lldb-cmake/
will revert if the error reappears

Differential Revision: https://reviews.llvm.org/D56084

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@350290 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed