Added string literal helper function to obtain the type
attributed by a constant address space.
Also fixed predefind __func__ expr to use the helper
to constract the string literal correctly.
Differential Revision: https://reviews.llvm.org/D46049
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@331877 91177308-0d34-0410-b5e6-96231b3b80d8
Anastasia Stulova