To install it on Debian:
- download the file kamailio.syntax from here
- copy it to /usr/share/mc/syntax
- then add to the file /usr/share/mc/syntax/Syntax including:
file ..\*\\.cfg$ Kamailio\sconfig
To enable it enable it only for your user, add above two line to ~/.mc/cedit/Syntax.
An update for version 3.0.x should follow soon.
Here is an screenshot taken on Mac OS X: