Dependent Address Space Support

Dependent Address Space Support

This patch relates to: https://reviews.llvm.org/D33666 This adds support
for template parameters to be passed to the address_space attribute.
The main goal is to add further flexibility to the attribute and allow
for it to be used easily with templates.

The main additions are a new type (DependentAddressSpaceType) alongside
its TypeLoc and its mangling. As well as the logic required to support
dependent address spaces which mainly resides in TreeTransform.h and
SemaType.cpp.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@314649 91177308-0d34-0410-b5e6-96231b3b80d8