[AST] Move operations enum to a definition file.

Summary:
This patch moves the enum definitions to a definition (.def) file.

These modifications provide way to list enumerators of a given type.

As an example, this allow parsing of "kinds" in the dynamic matchers.
see: http://reviews.llvm.org/D19871
The dynamic matcher "ofKind" also required this patch to be fixed.

Reviewers: klimek, aaron.ballman, rsmith

Subscribers: klimek, sbenza, alexfh, cfe-commits

Differential Revision: http://reviews.llvm.org/D20207

llvm-svn: 269347