Add a SELFRELOC kernel option for the sake of documentation clarity.

Instead of telling that x86/boot(8) reloc command needs a kernel able
to self relocate, we can tell it needs a kernel built with the
SELFRELOC option. This keeps the reader from wondering what could
make a kernel able to self relocate.

branches: 1.12.20;
Merge the bouyer-xenpvh branch, bringing in Xen PV drivers support under HVM
guests in GENERIC.
Xen support can be disabled at runtime with
boot -c
disable hypervisor

branches: 1.11.20; 1.11.26;
white space police

branches: 1.10.2;
bump CHILD_MAX and OPEN_MAX defaults on several platforms, both to 1024.

branches: 1.9.12; 1.9.14;
Remove bpf_jit which was ported from FreeBSD recently.

It will soon be replaced with the new bpfjit kernel module.

branches: 1.8.2;
Add BPF JIT compiler, currently supporting amd64 and i386. Code obtained
from FreeBSD. Also, make few BPF fixes and simplifications while here.
Note that bpf_jit_enable is false for now.

OK dyoung@, some feedback from matt@

Import config(9) file and register HAL's files in the build machinery.

branches: 1.6.6; 1.6.8; 1.6.10; 1.6.16;
Shuffle ioapic/mainbus/cpu into std.amd64 like i386.

Require MULTIPROCESSOR. PR kern/38537.

branches: 1.4.6; 1.4.8; 1.4.10;
Refactor in_cksum/in4_cksum/in6_cksum implementations:
- All three functions are included in the kernel by default.
They call a backend function cpu_in_cksum after possibly
computing the checksum of the pseudo header.
- cpu_in_cksum is the core to implement the one-complement sum.
The default implementation is moderate fast on most platforms
and provides a 32bit accumulator with 16bit addends for L32 platforms
and a 64bit accumulator with 32bit addends for L64 platforms.
It handles edge cases like very large mbuf chains (could happen with
native IPv6 in the future) and provides a good base for new native
implementations.
- Modify i386 and amd64 assembly to use the new interface.

This disables the MD implementations on !x86 until the conversion is
done. For Alpha, the portable version is faster.

branches: 1.3.50; 1.3.56;
merge ktrace-lwp.

include "conf/std".

branches: 1.1.2; 1.1.18;
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.