Do not use @allow-recursion. In its current form the macro is not
recursive.
@c Output various FIXME information only in PROOF rendition.
@macro FIXME{string}
-@allow-recursion
-@quote-arg
@ifset PROOF
@ifset PROOF_FOOTNOTED
@footnote{@strong{FIXME:} \string\}
@end macro
@macro FIXME-ref{string}
-@quote-arg
@ifset PROOF
@strong{<REF>} \string\ @strong{</>}
@end ifset
@end macro
@macro FIXME-pxref{string}
-@quote-arg
@ifset PROOF
@strong{<PXREF>} \string\ @strong{</>}
@end ifset
@end macro
@macro FIXME-xref{string}
-@quote-arg
@ifset PROOF
@strong{<XREF>} \string\ @strong{</>}
@end ifset