systemc: Fix a typo/bug in sc_int_base.hh.

When being turned into gem5 coding style, a pair of "!" operators were
dropped, reversing the behavior of the functions involved.

Change-Id: Ife795c22aff953c5ab592e7baa3a5e1c15e63c84
Reviewed-on: https://gem5-review.googlesource.com/c/12591
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

Systemc: Port over all of the systemc "datatype" headers.

These are the headers originally written by Accellera with a few
modifications. Most significantly, I went through and mostly (but not
entirely) manually editted them to conform to gem5 style and to be
more self consistent. Second, I resolved some macros which optionally
select features. I removed support for deprecated functions, and
otherwise enabled everything.

The actual implementation behind these headers will also be ported
over, but in a subsequent change.

Change-Id: I203d3f6c8a3af9120b946001d01defbb0643a6b6
Reviewed-on: https://gem5-review.googlesource.com/10843
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>