Move CodegenAnyVal to its own file.

This is needed by upcoming commits so we can #include anyval-util.h in
cross-compiled functions without pulling in all of LLVM in our IR
module (this causes build problems, plus our module will be huger than
necessary).

Change-Id: I756d5a95e5c254403d9ad5684fe27cf96f3aec1e
Reviewed-on: http://gerrit.ent.cloudera.com:8080/2677
Reviewed-by: Nong Li <nong@cloudera.com>
Tested-by: jenkins