[ScopBuilder] Move canonicalizeDynamicsBasePtrs from ScopInfo. NFC.

Refactor Scop and ScopBuilder class. Move canonicalizeDynamicsBasePtrs
and corresponding static functions from ScopInfo.cpp to ScopBuilder.cpp

Patch by Dominik Adamski <adamski.dominik@gmail.com>

Differential Revision: https://reviews.llvm.org/D62781

llvm-svn: 362554