Syntax for GDB (session?) could be updated

[ratijas]

Syntax definition could be updated to use newer yaml based language, and to highlight backtraces like the real gdb does in a terminal (which is basically the reason I found this plugin in the first place).

The good thing is, even though these tracktraces include C++ function signatures, actually they are very limited compared to the full C++ language, and it also doesn't have to deal with partial input in a very robust way.

I might or might not do it myself, depends on my free time and impulse. But I will, I'd post a note here first.