[temp] Add note around example to explain what it's an example of, and

add missing paragraph numbers.

Author: zygoloid

source/templates.tex

@@ -64,6 +64,7 @@
 \tcode{>{>}} token by two consecutive \tcode{>}
 tokens~(\ref{temp.names}).\end{note}
 
+\pnum
 The
 \grammarterm{declaration}
 in a
@@ -84,6 +85,7 @@
 \item be an \grammarterm{alias-declaration}.
 \end{itemize}
 
+\pnum
 A \grammarterm{template-declaration} is a \grammarterm{declaration}.
 \indextext{template!definition of}%
 A \grammarterm{template-declaration} is also a definition
@@ -205,12 +207,18 @@
 \grammarterm{constraint-expression}.
 The \grammarterm{constraint-logical-or-expression} of a
 \grammarterm{requires-clause} is an unevaluated operand (Clause~\ref{expr}).
+\begin{note}
+The expression in a \grammarterm{requires-clause}
+uses a restricted grammar to avoid ambiguities.
+Parentheses can be used to specify arbitrary expressions
+in a \grammarterm{requires-clause}.
 \begin{example}
 \begin{codeblock}
 template<int N> requires N == sizeof unsigned short
 int f();    // error: parentheses required around \tcode{==} expression
 \end{codeblock}
 \end{example}
+\end{note}
 
 \pnum
 A function template, member function of a class template, variable template,