systemc: Improve handling of empty process handles.

Most had checks, but didn't print any message. throw_it needed a check
as well.

Change-Id: I916c837112f9b27852583f01b3e16a6f53d5e7ca
Reviewed-on: https://gem5-review.googlesource.com/c/12440
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Implement most of the sc_report_handler mechanism.

This doesn't include support for the deprecated integer message ids.

Change-Id: I309d58df1cdc464428189eb0b7180edf41ca4f67
Reviewed-on: https://gem5-review.googlesource.com/12048
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Add support for deprecated integer report handler ids.

These are deprecated but still used in the regression tests.

Change-Id: Id59cf950fbe0530a6cdce20a256d450b243f12d3
Reviewed-on: https://gem5-review.googlesource.com/11256
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Stub out all the standard utilility classes and functions.

Change-Id: I9e9724edb6281e0b0a6bae5546b0ede77d295c12
Reviewed-on: https://gem5-review.googlesource.com/10841
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>