[meta.logical] Improve formatting for consistency with other library

clauses.

Author: zygoloid

source/utilities.tex

@@ -10559,11 +10559,12 @@
 This subclause describes type traits for applying logical operators
 to other type traits.
 
-\pnum
-\begin{codeblock}
-  template<class... B> struct conjunction : @\seebelow@ { };
-\end{codeblock}
+\indexlibrary{\idxcode{conjunction}}%
+\begin{itemdecl}
+template<class... B> struct conjunction : @\seebelow@ { };
+\end{itemdecl}
 
+\begin{itemdescr}
 \pnum
 The class template \tcode{conjunction}
 forms the logical conjunction of its template type arguments.
@@ -10591,12 +10592,14 @@
 does not require the instantiation of \tcode{Bj::value} for \tcode{j > i}.
 \enternote This is analogous to the short-circuiting behavior of \tcode{\&\&}.
 \exitnote
+\end{itemdescr}
 
-\pnum
-\begin{codeblock}
-  template<class... B> struct disjunction : @\seebelow@ { };
-\end{codeblock}
+\indexlibrary{\idxcode{disjunction}}%
+\begin{itemdecl}
+template<class... B> struct disjunction : @\seebelow@ { };
+\end{itemdecl}
 
+\begin{itemdescr}
 \pnum
 The class template \tcode{disjunction}
 forms the logical disjunction of its template type arguments.
@@ -10623,17 +10626,20 @@
 does not require the instantiation of \tcode{Bj::value} for \tcode{j > i}.
 \enternote This is analogous to the short-circuiting behavior of \tcode{||}.
 \exitnote
+\end{itemdescr}
 
-\pnum
-\begin{codeblock}
-  template<class B> struct negation : bool_constant<!B::value> { };
-\end{codeblock}
+\indexlibrary{\idxcode{negation}}%
+\begin{itemdecl}
+template<class B> struct negation : bool_constant<!B::value> { };
+\end{itemdecl}
 
+\begin{itemdescr}
 \pnum
 The class template \tcode{negation}
 forms the logical negation of its template type argument.
 The type \tcode{negation<B>}
 is a UnaryTypeTrait with a BaseCharacteristic of \tcode{bool_constant<!B::value>}.
+\end{itemdescr}
 
 \rSec1[ratio]{Compile-time rational arithmetic}