Merge IRAccess into MemoryAccess

All MemoryAccess objects will be owned by ScopInfo::AccFuncMap which 
previously stored the IRAccess objects. Instead of creating new 
MemoryAccess objects, the already created ones are reused, but their 
order might be different now. Some fields of IRAccess and MemoryAccess 
had the same meaning and are merged.

This is the last step of fusioning TempScopInfo.{h|cpp} and 
ScopInfo.{h.cpp}. Some refactoring might still make sense.

Differential Revision: http://reviews.llvm.org/D12843

llvm-svn: 248024