[FileCheck] Move private interface to its own header
Summary:
Most of the class definition in llvm/include/llvm/Support/FileCheck.h
are actually implementation details that should not be relied upon. This
commit moves all of it in a new header file under
llvm/lib/Support/FileCheck. It also takes advantage of the code movement
to put the code into a new llvm::filecheck namespace.
Reviewers: jhenderson, chandlerc, jdenny, probinson, grimar, arichardson, rnk
Subscribers: hiraditya, llvm-commits, probinson, dblaikie, grimar, arichardson, tra, rnk, kristina, hfinkel, rogfer01, JonChesterfield
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D67649
llvm-svn: 373395