Implement P0482R2, support for char8_t type.

This is not yet part of any C++ working draft, and so is controlled by the flag
-fchar8_t rather than a -std= flag. (The GCC implementation is controlled by a
flag with the same name.)

This implementation is experimental, and will be removed or revised
substantially to match the proposal as it makes its way through the C++
committee.

llvm-svn: 331244
diff --git a/clang/lib/AST/NSAPI.cpp b/clang/lib/AST/NSAPI.cpp
index 8adaef1..eb807f0 100644
--- a/clang/lib/AST/NSAPI.cpp
+++ b/clang/lib/AST/NSAPI.cpp
@@ -436,6 +436,7 @@
   case BuiltinType::Void:
   case BuiltinType::WChar_U:
   case BuiltinType::WChar_S:
+  case BuiltinType::Char8:
   case BuiltinType::Char16:
   case BuiltinType::Char32:
   case BuiltinType::Int128: