Rewrite eachOf/allOf/anyOf to use a variadic operator.

Summary:
Rewrite eachOf/allOf/anyOf to use a variadic operator, instead of hand-written calls to Polymorphic matchers.
This simplifies their definition and future changes to add them to the dynamic registry.

Reviewers: klimek

CC: cfe-commits, revane

Differential Revision: http://llvm-reviews.chandlerc.com/D1427