Somewhere between bison versions 3.5 and 3.6.4, having multiple characters in a single-quoted string went from a warning to an error. This commit corrects that by changing a literal to string,
@@ -233,7 +233,7 @@ rules
| rules rule
| rules import
| rules error rule /* on error skip until next rule..*/
- | rules error 'include' /* .. or include statement */
+ | rules error "include" /* .. or include statement */
;