In error list lexer, detect lines that start with "+++ " as diff messages rather than additions.
In error list lexer, detect lines that start with "+++ " as diff messages
rather than additions.

rhaberkorn/scintilla-mirror,rhaberkorn/scintilla-mirror,rhaberkorn/scintilla-mirror,rhaberkorn/scintilla-mirror,rhaberkorn/scintilla-mirror,rhaberkorn/scintilla-mirror,rhaberkorn/scintilla-mirror,rhaberkorn/scintilla-mirror