coreserver: Improve message buffering

Signed-off-by: Michael Buesch <m@bues.ch>
Port GUI to coreserver-API

Signed-off-by: Michael Buesch <m@bues.ch>
gui: Handle server messages with timeout

Signed-off-by: Michael Buesch <m@bues.ch>
gui: Only dump visible instructions

Signed-off-by: Michael Buesch <m@bues.ch>
gui: Do insn dump state update asynchronously

Signed-off-by: Michael Buesch <m@bues.ch>
gui: Prune old CPU stats

Signed-off-by: Michael Buesch <m@bues.ch>
gui: Simplify stats drawing

Signed-off-by: Michael Buesch <m@bues.ch>
gui: Fix edit widget font

Signed-off-by: Michael Buesch <m@bues.ch>