This change ensures that the libclang CXCursor represents the CoroutineBody
and the Coreturn statement using the appropriate CXCursor_UnexposedStmt kind
instead of CXCursor_UnexposedExpr. The problem with CXCursor_UnexposedExpr is
that the consumer functions assumed that CoroutineBody/Coreturn statements
were valid expressions and performed an invalid downcast to Expr causing
assertion failures or other crashes.
rdar://40204290
llvm-svn: 350282