[locale.codecvt.virtuals] Use code font for integer literals.

Author: jwakely

source/locales.tex

@@ -2670,10 +2670,10 @@
 \begin{itemdescr}
 \pnum
 \returns
--1 if the encoding of the \tcode{externT} sequence is state-dependent; else the
+\tcode{-1} if the encoding of the \tcode{externT} sequence is state-dependent; else the
 constant number of \tcode{externT} characters needed to produce an internal
-character; or 0 if this number is not a constant.\footnote{If \tcode{encoding()}
-yields -1, then more than \tcode{max_length()} \tcode{externT} elements
+character; or \tcode{0} if this number is not a constant.\footnote{If \tcode{encoding()}
+yields \tcode{-1}, then more than \tcode{max_length()} \tcode{externT} elements
 may be consumed when producing a single \tcode{internT} character, and additional
 \tcode{externT} elements may appear at the end of a sequence after those that
 yield the final \tcode{internT} character.}