interface: handle replacement of InputKind::C by Language::C
interface: handle replacement of InputKind::C by Language::C

In particular, LLVM commit 09d890d728e extracted Language from InputKind
and made it available as a top-level enum in clang/Basic/LangStandard.h.

Reported-by: Rainer Orth <eed1903a65fb51375c9a57c0d5925ebe4056dcab@gcc.gnu.org>
Signed-off-by: Sven Verdoolaege <235c10dd23b819f81cdc9756a251746bc184cab6@gmail.com>

Meinersbur/isl,Meinersbur/isl,Meinersbur/isl,Meinersbur/isl