Refactoring cl::parser construction and initialization.

Summary:
Some parsers need references back to the option they are members of. This is used for handling the argument string as well as by the various pass name parsers for making pass names into flags.

Making parsers that need to refer back to the option have a reference to the option eliminates some of the members of various parsers, and enables further code cleanup.

Reviewers: dexonsmith

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D7131

llvm-svn: 226864