Support return type deduction for templates in -fdelayed-template-parsing (microsoft) mode

Please see http://llvm-reviews.chandlerc.com/D2053 for discussion and Richard's stamp.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@193849 91177308-0d34-0410-b5e6-96231b3b80d8