[Geany-devel] Use GtkBuilder

[Lex Trotman]

Thanks Matthew, Jiri,

I was not after doing GTK3 it immediately, just trying to see if there
were things being done in moving to gtkbuilder that might need to be
undone later, and could we avoid that.

>From both your comments it appears to be no extra work, gtkbuilder is
purely a step on the way to gtk3.  Thats good, its a big monolithic
change all ready. It is good it doesn't need to grow.

IIUC gtk3 ready migrations can then happen in small pieces afterwards.
 The smaller the resolution the more useful git blame is :)

Cheers
Lex