gdb: add remote_state::{is_async_p,can_async_p}

A subsequent patch will want to know if the remote is async within a
remote_state method.  Add a helper method for that, and for "can async"
as well, for symmetry.

Change-Id: Id0f648ee4896736479fa942f5453eeeb0e5d4352
Approved-By: Andrew Burgess <aburgess@redhat.com>
1 file changed