- fix _C_LABEL so that it actually works.
- make __RENAME use _C_LABEL.
- fix __RENAME so that it expects an unquoted argument.
- fix __indr_reference and __warn_references so that they
supply their own final semicolon.
- define __warn_references to nothing if not GNU C (required
by the way it's used).
The __warn_references semicolon change has to be made
so that __warn_references can be defined into nothing.
(A ; all by itself isn't a great idea.) The __indr_reference
change was made for consistency.