[styles] Allow 'listings' package v1.8c (#3592)

Author: rogerorr

source/styles.tex

@@ -142,13 +142,13 @@
 %% (copied verbatim from listings.sty version 1.6 except where commented)
 \makeatletter
 
-\lst@CheckVersion{1.8b}{\lst@CheckVersion{1.7}{\lst@CheckVersion{1.6}{\lst@CheckVersion{1.5b}{
+\lst@CheckVersion{1.8c}{\lst@CheckVersion{1.8b}{\lst@CheckVersion{1.7}{\lst@CheckVersion{1.6}{\lst@CheckVersion{1.5b}{
  \typeout{^^J%
  ***^^J%
  *** This file requires listings.sty version 1.6.^^J%
  *** You have version \lst@version; exiting ...^^J%
  ***^^J}%
- \batchmode \@@end}}}}
+ \batchmode \@@end}}}}}
 
 \def\lst@Init#1{%
     \begingroup