[zombie.names] Reformatted sequence of zombie header as a list

This reformatting, in addition being consistent with the rest of
the clause, resolves an overful hbox warning.

Also added the missing text at end of the opening sentence
of p3.

Author: AlisdairM

source/lib-intro.tex

@@ -3098,22 +3098,25 @@
 \pnum
 The following names are reserved as member functions for previous
 standardization, and may not be used as a name for function-like macros in
+portable code:
 \begin{itemize}
 \item \indexlibraryzombie{freeze} \tcode{freeze},
 \item \indexlibraryzombie{pcount} \tcode{pcount}, and
 \item \indexlibraryzombie{stossc} \tcode{stossc},
 \end{itemize}
 
 \pnum
-The header names
-\libnoheader{ccomplex},
-\libnoheader{ciso646},
-\libnoheader{codecvt},
-\libnoheader{cstdalign},
-\libnoheader{cstdbool},
-\libnoheader{ctgmath}, and
-\libnoheader{strstream}
-are reserved for previous standardization.
+The following header names are reserved for previous standardization:
+\begin{itemize}
+\item \libnoheader{ccomplex},
+\item \libnoheader{ciso646},
+\item \libnoheader{codecvt},
+\item \libnoheader{cstdalign},
+\item \libnoheader{cstdbool},
+\item \libnoheader{ctgmath},
+and
+\item \libnoheader{strstream}
+\end{itemize}
 
 \rSec4[macro.names]{Macro names}