Replace remaining uses of \nonterminal with \grammarterm.

Fixes #1312.

Author: tkoeppe

source/declarators.tex

@@ -848,7 +848,7 @@
 then the type of the identifier of
 \tcode{D}
 is ``\placeholder{derived-declarator-type-list} \grammarterm{cv-qualifier-seq} pointer to member of class
-\nonterminal{nested-name-specifier} of type
+\grammarterm{nested-name-specifier} of type
 \tcode{T}''.
 The optional \grammarterm{attribute-specifier-seq}~(\ref{dcl.attr.grammar}) appertains to the 
 pointer-to-member.

source/lex.tex

@@ -1428,7 +1428,7 @@
 \begin{bnftab}
 \nontermdef{r-char}\br
 \>\textnormal{any member of the source character set, except}\br
-\>\>\textnormal{a right parenthesis \terminal{)} followed by the initial \nonterminal{d-char-sequence}}\br
+\>\>\textnormal{a right parenthesis \terminal{)} followed by the initial \grammarterm{d-char-sequence}}\br
 \>\>\textnormal{(which may be empty) followed by a double quote \terminal{"}.}
 \end{bnftab}
 

source/preprocessor.tex

@@ -196,7 +196,7 @@
 
 \begin{ncbnf}
 \nontermdef{h-preprocessing-token}\br
-    \textnormal{any \nonterminal{preprocessing-token} other than \terminal{>}}
+    \textnormal{any \grammarterm{preprocessing-token} other than \terminal{>}}
 \end{ncbnf}
 
 \begin{ncbnf}