Fix whitespace in example of bad indentation: a comment indicated that one

line was not indented at all, so the example is no longer indented at all.
All of the errors being shown remain.

Typo: characteru --> character

Doc/ref/ref2.tex

@@ -327,7 +327,7 @@ String literals are described by the following lexical definitions:
   \production{shortstringchar}
              {<any ASCII character except "\e" or newline or the quote>}
   \production{longstringchar}
-             {<any ASCII characteru except "\e">}
+             {<any ASCII character except "\e">}
   \production{escapeseq}
              {"\e" <any ASCII character>}
 \end{productionlist}