[diff.offsetof] Better index usage of the offsetof macro

source/compatibility.tex

@@ -2395,7 +2395,7 @@
 Support for new thread facilities.
 \effect
 Valid but implementation-specific \CppIII{} code that relies on
-\tcode{errno} being the same across threads may change behavior in this
+\tcode{\libmacro{errno}} being the same across threads may change behavior in this
 revision of \Cpp{}.
 
 \rSec2[diff.cpp03.utilities]{\ref{utilities}: general utilities library}
@@ -3734,10 +3734,9 @@
 Subclause \ref{csetjmp.syn} describes the changes.
 
 \rSec3[diff.offsetof]{Macro \tcode{offsetof(\placeholder{type}, \placeholder{member-designator})}}
-\indexlibraryglobal{offsetof}%
 
 \pnum
-The macro \tcode{offsetof}, defined in
+The macro \tcode{\libmacro{offsetof}}, defined in
 \libheaderref{cstddef},
 accepts a restricted set of \tcode{\placeholder{type}} arguments in \Cpp{}.
 Subclause \ref{support.types.layout} describes the change.