Add a COMMENT describing what each component roughly does.

"make describe" prints the comment.

Requested/inspired by Vincent Schwarzer on rumpkernel-users

branches: 1.2.4; 1.2.8; 1.2.10;
rename component.c -> netinet6_component.c

branches: 1.1.2;
Separate inet and inet6, allows inet6-only rump kernels.

remove ip{,6}_id.c

branches: 1.5.16;
Move udp6_output() into udp6_usrreq.c, and remove udp6_output.c. This is
more consistent with IPv4, and there is no good reason for keeping a
separate file only for one function. FreeBSD did the same.

Rumpify netipsec

Note that we should modularize netipsec and reduce reverse symbol references
(referencing symbols of netipsec from net, netinet and netinet6) though,
the task needs lots of code changes. Prior to doing so, rumpifying it and
having ATF tests should be useful.

branches: 1.3.2; 1.3.4;
some final -Ifoo/opt removal

Move defines of INET and INET6 from opt_inet.h to Makefile.inc

As discussed with pooka@
fixes current issues with ipv6 on rump being broken

branches: 1.1.2; 1.1.6; 1.1.10; 1.1.12;
Separate inet and inet6, allows inet6-only rump kernels.

rename component.c -> netinet6_component.c

Register netisr's from component constructors instead of via a hardcoded
global list.

Allow kernels compiled with INET+INET6 to be booted as IPv4-only or IPv6-only.

branches: 1.2.2;
Partially revert previous, there are still a few gotchas in
running ipv4/ipv6-only (too many dependencies on ifdefs).

Separate inet and inet6, allows inet6-only rump kernels.

Garbage-collect the remaining vestiges of netisr.

Don't call loopinit() here. Instead panic if -lrumpnet_net has not been
called to initialize lo0ifp.

more loopinit();

Put the kernelside rump kernel headers into <rump-sys> instead of
sprinkling them around the faction directories. Avoids having
to add a CPPFLAGS (or several) to pretty much every component
Makefile.

Leave compat headers around in the old locations.

The commit changes some autogenerated files, but I'll fix the
generators shortly and regen.

branches: 1.3.2;
Nuke the DOMAINADD() macro and just call domain_attach(), now that things
work correctly that way.

branches: 1.2.4;
- Implement pktqueue interface for lockless IP input queue.
- Replace ipintrq and ip6intrq with the pktqueue mechanism.
- Eliminate kernel-lock from ipintr() and ip6intr().
- Some preparation work to push softnet_lock out of ipintr().

Discussed on tech-net.

branches: 1.1.2; 1.1.4; 1.1.6;
rename component.c -> netinet6_component.c

Remove shlib_version files and just use Makefile SHLIB_MAJOR/MINOR,
with the default provided by Makefile.rump (they're all 0.0 anyway)

branches: 1.1.2; 1.1.6; 1.1.10; 1.1.12;
Separate inet and inet6, allows inet6-only rump kernels.