Instantiation bug fix extension (cf. r184503) -- minor code fixes, including a typo that caused a runtime assertion after firing diagnosis for class definitions, with the 'template' keyword as template header, in friend declarations.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@184634 91177308-0d34-0410-b5e6-96231b3b80d8