This script first runs the regular gdb's 'bt' command, and then if we are in a
coroutine it prints the coroutines backtraces in the order in which they
were called.

Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Message-Id: <20201217155436.927320-3-mlevitsk@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>