If an attribute has a semantically meaningful spelling (such as ArgumentWithTypeTagAttr or MSInheritanceAttr), display the spelling used for the attribute as part of the AST dump. This should ease debugging the AST for these attributes. Attributes without semantically meaningful spelling variations are not affected.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@199834 91177308-0d34-0410-b5e6-96231b3b80d8