CWG3076 Remove unnecessary IFNDR for malformed header-name-tokens

Author: eisenwave

source/lex.tex

@@ -1795,10 +1795,15 @@
 \indextext{literal!string}%
 \begin{bnf}
 \nontermdef{string-literal}\br
-    \opt{encoding-prefix} \terminal{"} \opt{s-char-sequence} \terminal{"}\br
+    \opt{encoding-prefix} plain-string-literal\br
     \opt{encoding-prefix} \terminal{R} raw-string
 \end{bnf}
 
+\begin{bnf}
+\nontermdef{plain-string-literal}\br
+    \terminal{"} \opt{s-char-sequence} \terminal{"}
+\end{bnf}
+
 \begin{bnf}
 \nontermdef{s-char-sequence}\br
     s-char \opt{s-char-sequence}

source/preprocessor.tex

@@ -757,6 +757,9 @@
 in the directive are processed just as in normal text
 (i.e., each identifier currently defined as a macro name is replaced by its
 replacement list of preprocessing tokens).
+After replacement,
+if the first preprocessing token is a \grammarterm{string-literal},
+it shall be a \grammarterm{plain-string-literal}.
 Then, an attempt is made to form a \grammarterm{header-name}
 preprocessing token\iref{lex.header} from the whitespace and the characters
 of the spellings of the resulting sequence of preprocessing tokens;