base,sim,ext: Adding GDB signals definition

GDB proposes a signal definition that is not necessarily identical
to the kernel's. To not lost GDB, we need to add this definition
 (in ext/remotegdb/signals.hh) and replace the linux signals everywhere
where they where used to interact with GDB.
 (otherwise it doesn't recognize some trap reasons).

Change-Id: I2bbfee36313cc766549000cf197c23c2561ea5f9
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/63534
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Reviewed-by: Quentin Forcioli <quentin.forcioli@telecom-paris.fr>
Tested-by: kokoro <noreply+kokoro@google.com>
9 files changed