Emacs GDB/MI migration

by Dmitry Dzhus for GNU Project

The goal of this project is to migrate the GDB graphical interface in Emacs to completely use GDB's Machine Interface (GDB/MI). Currently a mixture of GDB annotations and GDB/MI are used to provide GDB UI in Emacs. Dropping deprecated annotations in favor of machine-oriented GDB/MI protocol will make underlying codebase more robust and easier to maintain and improve. Switching to GDB/MI will also allow using new features of GDB from Emacs.