[diff.cpp17.library] Fix description of how to adjust code for the

removal of <ccomplex> and <ctgmath>.

Author: zygoloid

source/compatibility.tex

@@ -2001,7 +2001,23 @@
 \tcode{<cstdalign>},
 \tcode{<cstdbool>}, and
 \tcode{<ctgmath>}.
-The \tcode{\#include} directives can simply be removed with no loss of meaning.
+To retain the same behavior:
+\begin{itemize}
+\item
+a \tcode{\#include} of \tcode{<ccomplex>} can be replaced by
+a \tcode{\#include} of \tcode{<complex>}\iref{complex.syn},
+\item
+a \tcode{\#include} of \tcode{<ctgmath>} can be replaced by
+a \tcode{\#include} of \tcode{<cmath>}\iref{cmath.syn} and
+a \tcode{\#include} of \tcode{<complex>},
+and
+\item
+a \tcode{\#include} of
+\tcode{<ciso646>},
+\tcode{<cstdalign>}, or
+\tcode{<cstdbool>}
+can simply be removed.
+\end{itemize}
 
 \rSec2[diff.cpp17.containers]{\ref{containers}: containers library}