[diff.cpp03.library] Fix cross-reference to restriction on macro names

Author: AlisdairM

source/compatibility.tex

@@ -2361,7 +2361,7 @@
 \CppIII{} code that uses a top-level namespace \tcode{posix} may be invalid in
 this revision of \Cpp{}.
 
-\diffref{res.on.macro.definitions}
+\diffref{macro.names}
 \change
 Additional restrictions on macro names.
 \rationale