fixup: xref for translation character set

Author: jensmaurer

source/lex.tex

@@ -69,8 +69,8 @@
 \indextext{character set!basic source}%
 Physical source file characters are mapped, in an
 \impldef{mapping physical source file characters to translation character set} manner,
-to the translation character set (introducing new-line characters for end-of-line
-indicators).
+to the translation character set\iref{lex.charset}
+(introducing new-line characters for end-of-line indicators).
 The set of physical source file characters accepted is \impldef{physical source file
 characters}.
 \item