[temp.res.commit] Add introduction of definition of "type-only context".

This avoids having to style either of the two subsequent
sub-definitions as the main definition.

Author: tkoeppe

source/templates.tex

@@ -4888,9 +4888,9 @@
 
 \pnum
 \indextext{type-only!context|see{context, type-only}}%
+A \defnx{type-only context}{context!type-only} is defined as follows:
 A qualified or unqualified name is said to be in
-a \defnx{type-only context}{context!type-only}
-if it is the terminal name of
+a type-only context if it is the terminal name of
 \begin{itemize}
 \item a
 \grammarterm{typename-specifier},