- In sendsig() and sigaction1(), don't hard-code signal trampoline
versions. Instead, use the version constants from <sys/signal.h>
and automatically (and correctly) handle cases where multiple versions
of a particular trampoline flavor exist. Conditionalize support
for sigcontext trampolines on __HAVE_STRUCT_SIGCONTEXT.
- aarch64 and amd64 don't use sigcontext natively, but do need to
support it for 32-bit compatibility; define __HAVE_STRUCT_SIGCONTEXT
conditionally on _KERNEL.

This is included into user-programs by signal.h, it shouldn't be
pulling in machine/fpu.h - which doesn't describe anything userspace
(directly) needs.

branches: 1.11.16; 1.11.26;
Make the emulations, exec formats, coredump, NFS, and the NFS server
into modules. By and large this commit:

- shuffles header files and ifdefs
- splits code out where necessary to be modular
- adds module glue for each of the components
- adds/replaces hooks for things that can be installed at runtime

branches: 1.10.2;
put the contents of these header files around #ifdef __x86_64__, and
#include the <i386/foo.h> in the #else clause, making these files
largely bit-size independant.

branches: 1.9.42; 1.9.46; 1.9.52;
Accept the old ABI versions of signal trampolines for 32-bit
compatibility. Unbreaks the i386 cvsup binary on amd64.

Problem reported by Blair Sadewitz and Viktor Holmlund, fix tested by
Viktor Holmlund.

branches: 1.8.24; 1.8.26;
merge ktrace-lwp.

branches: 1.7.10; 1.7.12;
SIGTRAMP_VALID() should not pollute the user namespace

only accept signal trampoline version 2, and remove "struct sigcontext"

bye, bye _MCONTEXT_TO_SIGCONTEXT and vice versa.

Add SIGTRAMP_VALID().

Move UCB-licensed code from 4-clause to 3-clause licence.

Patches provided by Joel Baker in PR 22364, verified by myself.

branches: 1.2.2;
Add a new feature-test macro, _NETBSD_SOURCE. If this is defined
by the application, all NetBSD interfaces are made visible, even
if some other feature-test macro (like _POSIX_C_SOURCE) is defined.
<sys/featuretest.h> defined _NETBSD_SOURCE if none of _ANSI_SOURCE,
_POSIX_C_SOURCE and _XOPEN_SOURCE is defined, so as to preserve
existing behaviour.

This has two major advantages:
+ Programs that require non-POSIX facilities but define _POSIX_C_SOURCE
can trivially be overruled by putting -D_NETBSD_SOURCE in their CFLAGS.
+ It makes most of the #ifs simpler, in that they're all now ORs of the
various macros, rather than having checks for (!defined(_ANSI_SOURCE) ||
!defined(_POSIX_C_SOURCE) || !defined(_XOPEN_SOURCE)) all over the place.

I've tried not to change the semantics of the headers in any case where
_NETBSD_SOURCE wasn't defined, but there were some places where the
current semantics were clearly mad, and retaining them was harder than
correcting them. In particular, I've mostly normalised things so that
_ANSI_SOURCE gets you the smallest set of stuff, then _POSIX_C_SOURCE,
_XOPEN_SOURCE and _NETBSD_SOURCE in that order.

Tested by building for vax, encouraged by thorpej, and uncontested in
tech-userlevel for a week.

Rename the x86_64 port to amd64, as this is the actual name used for
the processor family now. x86_64 is kept as the MACHINE_ARCH value,
since it's already widely used (by e.g. the toolchain, etc), and
by other operating systems.