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.

Add a COMMENT describing what each component roughly does.

"make describe" prints the comment.

Requested/inspired by Vincent Schwarzer on rumpkernel-users

Make the cool syscall autogeneration feature work with the
newfangled r/o src feature.

factor out the syscall building code

regen and add a build target.

branches: 1.6.6;
rename component.c -> sys_linux_component.c

Build with IPv6 support.

Add now needed linux_pipe.c sources.

Add syscall wrapper for mknodat(2) to deal with PAD argument difference
between rump and linux versions.

branches: 1.2.6; 1.2.8;
If linux syscall emulation is linked in to a rump kernel, use it as the
default emulation.

branches: 1.1.2;
Add the first attempt at rump kernel support for Linux clients. This has
been lightly tested with unmodified networking applications with both
the client and server on a 64bit le host. Unlike the standard Linux
compat libs where args and syscalls are swizzled around, this compat
lib only massages the arg data types due to the assumption that syscall
numbers come from librumpclient (via librumphijack) and therefore match
the native NetBSD numbers.