systemc: Include boost/bind.hpp in the systemc header.

The systemc spec says that sc_bind, sc_ref and sc_cref macros should
expand to boost::bind, boost::ref, and boost::cref respectively, but
that it's "use is not mandantory". Unfortunately, the regression tests
use those macros without actually including the boost headers for
themselves, and so they won't compile without dragging in these boost
headers as a dependency.

This should be mostly ok to include here since gem5 itself shouldn't
include systemc, just the sub headers that systemc brings in. systemc
code which includes systemc *will* have a dependency on boost, but that
at least contains the new dependency somewhat.

Change-Id: I1877a1b7dae2952f30a9d577d778739abbe7ac3b
Reviewed-on: https://gem5-review.googlesource.com/11178
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>

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>

systemc: Add systemc and systemc.h header files.

These are the header files as defined by the standard, although some
predefined channel types and most of the sc_dt namespace have yet to be
stubbed out, and so those portions are excluded.

Change-Id: Ic70f887c06e591974a4265c820eb0fdfa740d19a
Reviewed-on: https://gem5-review.googlesource.com/10838
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Gabe Black <gabeblack@google.com>