Pass the PrintingPolicy when converting types to strings in template type
diffing.  This removes extra "struct"/"class" in the type names and gives
"bool" instead of "_Bool" for booleans.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@213912 91177308-0d34-0410-b5e6-96231b3b80d8