Broke out header file list reading into separate function. Moved options to front.  Removed some trailing spaces.

llvm-svn: 178182

llvm-svn: 178172

llvm-svn: 178164

Revised to use MemoryBuffer. Removed redundant llvm:: qualifiers.  Removed unnecessary c_str() calls.  Reformatted with clang-format.

llvm-svn: 178104

Revised to use file list path as reference path, or path provide by new -prefix option.  Revised to use LLVM option parser.

llvm-svn: 177959

llvm-svn: 176998

llvm-svn: 176883

Initial check in of Doug's modularize tool for checking header readiness for modules, plus some changes per review feedback:  Removed system headers, changed to use stream output, added file name in message.

llvm-svn: 176847