[streambuf.assign] clarify boolean expressions

Author: Eisenwave

source/iostreams.tex

@@ -3436,14 +3436,15 @@
 \begin{itemdescr}
 \pnum
 \ensures
+The following expressions yield \keyword{true}:
 \begin{itemize}
-\item \tcode{eback() == rhs.eback()}
-\item \tcode{gptr() == rhs.gptr()}
-\item \tcode{egptr() == rhs.egptr()}
-\item \tcode{pbase() == rhs.pbase()}
-\item \tcode{pptr() == rhs.pptr()}
-\item \tcode{epptr() == rhs.epptr()}
-\item \tcode{getloc() == rhs.getloc()}
+\item \tcode{eback() == rhs.eback()},
+\item \tcode{gptr() == rhs.gptr()},
+\item \tcode{egptr() == rhs.egptr()},
+\item \tcode{pbase() == rhs.pbase()},
+\item \tcode{pptr() == rhs.pptr()},
+\item \tcode{epptr() == rhs.epptr()}, and
+\item \tcode{getloc() == rhs.getloc()}.
 \end{itemize}
 
 \pnum