Devel fixes an ancient (minor) colorizer bug

[Edward K. Ream]

PR #4173 (merged into "devel") fixes an ancient colorizing bug. This bug is unrelated to recent work.

The PR fixes a tiny edge case: the colorizer should not colorize @language directives if @killcolor or @nocolor is in effect. The PR contains a one-line fix.

I discovered this bug by lucky accident while testing the performance of @killcolor.

And I mean really lucky. It only happened if the user inserted a line after the @language line!

Please continue to test "devel." Thanks.

Edward