Adding completion to gscb

[chuchiperriman]

Hi Quixotix,

I'm adding completion support to the plugin, you can add it to upstream if you like.

[manxon]

Hi Chuchi,

I was looking for a completion function filtering box, that is, that there is an input box at the top of the code browser tab where you write a part of the function and it filters in the functions or variables having that name, is this patch for doing so?

Julian