Thrift: Make use of get_true_type.

Thrift: Make use of get_true_type.

Summary:
We added a helper function for the generators: get_true_type,
which finds the actual type behind a series of typedefs
(though the compiler only supports one layer of typedefs now).
This change uses it everywhere we used to have that loop.
(It was a lot of places.)

Reviewed By: mcslee

Test Plan: test/ManyTypedefs.thrift

Revert Plan: ok

git-svn-id: https://svn.apache.org/repos/asf/incubator/thrift/trunk@665220 13f79535-47bb-0310-9956-ffa450edef68