systemc: Get rid of leftovers from unimplemented warnings past.

These warnings were removed when the functionality they warned about
was implemented, but there were some leftovers like unnecessary
includes and some helper functions which hid gem5 specific headers
from the ext directory.

Change-Id: Ic886ac0f1264687524e3a7b7eaab8836f318a5a2
Reviewed-on: https://gem5-review.googlesource.com/c/13398
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Use c++11 partial functions instead of boosts.

This creates a depenendency on c++11 which the headers otherwise avoid,
but gem5 itself already has a c++11 dependency and not a boost
dependency, and outside of having a local copy of boost (which
Accellera does) there isn't a good way to put the placeholder values
_1, _2, etc., into the custom sc_unnammed namespace.

Change-Id: I52ca4c1bc52bef6ff2c62e9f3c32af46f95244dc
Reviewed-on: https://gem5-review.googlesource.com/c/13193
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Implement signal based resets.

The implementation is based on sc_event sensitivities.

Also of note is that the way reset works in the Accellera
implementation isn't consistent with the spec. That says that
wait(int n) is supposed to be equivalent to calling wait() n times,
assuming n is greater than 0.

Instead, Accellera stores that count and then doesn't wake up the
process until the count is 0, decrementing it otherwise.

That means that when the process is in reset, it won't actually reset
for those intermediate wait()s which it would if wait() was called
repeatedly. Also, oddly, when a reset becomes asserted, it will clear
the count to 0 explicitly. That may have been an attempt to make the
behavior of wait(int n) match the spec, but it doesn't handle cases
where the reset is already set when wait(int n) is called.

Change-Id: I92f8e9a128e6618af94dc048ce570a4436e17e4b
Reviewed-on: https://gem5-review.googlesource.com/c/13186
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Implement SC_FORK, SC_JOIN, and SC_CJOIN.

SC_CJOIN is non-standard, but relied on by the Accellera tests.

Change-Id: Ia4ddcb1749a07891157a58398137e94fcaa8e815
Reviewed-on: https://gem5-review.googlesource.com/c/12615
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Implement much of sc_spawn.

This doesn't implement reset signals, although those aren't implemented
for static processes either yet.

Change-Id: I748a7f75b9b91774c91d969bc1ff5b07e1711aa3
Reviewed-on: https://gem5-review.googlesource.com/12044
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Partially implement SC_FORK and SC_JOIN.

These macros need to expand to some minimal amount of wrapping code to
make the regression tests syntactically legal and compile.

Change-Id: I0b5569704b129d9c315526fc3363ef846a1b5c65
Reviewed-on: https://gem5-review.googlesource.com/11184
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Stub out the sc_spawn related classes and functions.

Change-Id: I79f695cca97aaae9af324eb18cab073f42f0a193
Reviewed-on: https://gem5-review.googlesource.com/10837
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Gabe Black <gabeblack@google.com>