[Gm2] colour bugfixes to the error/warning/note in trunk

[Gaius Mulley]

Hello,

I've git pushed some changes which fix bugs in the colour error output.
Warnings also have different colour (which are mainly generated from the
range detection module).  Also introduced are note messages which occur
if the -Wstudents option is used and a variable looks like a keyword
(and same variable name in different nested scopes).  These notes are
designed for introductory programmers though,


regards,
Gaius