systemc: Switch to using predefined messages for channels.

Create and use predefined messages for channels which match the ones
Accellera uses.

Change-Id: I179214838bbd83604e50225926cdc6b5b1b16923
Reviewed-on: https://gem5-review.googlesource.com/c/13330
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Define the nonstandard sc_event_queue_port typedef.

Used in the tests.

Change-Id: Ic4b4a313b2bd02e5cb3ec07c4f7ee79219728881
Reviewed-on: https://gem5-review.googlesource.com/11262
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Add some deprecated features to sc_clock.*.

Add in two deprecated typedefs, and a deprecated constructor. These
are necessary to get the regressions to build.

Change-Id: Id8320a67c680acbca0abaee9898158ffd2678d67
Reviewed-on: https://gem5-review.googlesource.com/11183
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Add the deprecated sc_signal_out_if typedef.

This is needed by the regression tests.

Change-Id: I5666cf9ad445869e74edda857afd59ab7ece4f4c
Reviewed-on: https://gem5-review.googlesource.com/10955
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Stub out the predefined channels.

Change-Id: Ie030aad26875bd49e54981ec1e9076b7b5af6630
Reviewed-on: https://gem5-review.googlesource.com/10839
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Gabe Black <gabeblack@google.com>