The purpose of the OptionValidator is to determine, based on some
arbitrary set of conditions, whether or not a command option is
valid for a given debugger state. An example of this might be
to selectively disable or enable certain command options that
don't apply to a particular platform.
This patch contains no functional change, and does not actually
make use of an OptionValidator for any purpose yet. A follow-up
patch will begin to add the logic and users of OptionValidator.
Reviewed by: Greg Clayton, Jim Ingham
Differential Revision: http://reviews.llvm.org/D4369
llvm-svn: 212290