Added mechanism to modularize for doing a compilation precheck

to determine files that have comnpilation or dependency problems.
A new -display-file-lists option use this to display lists of good files
(no compile errors), problem files, and a combined list with
problem files preceded by a '#'.  The problem files list can be
used in the module map generation assistant mode to exclude
problem files.  The combined files list can be used during module
map development.  See added docs.

llvm-svn: 241880