Add a COMMENT describing what each component roughly does.

"make describe" prints the comment.

Requested/inspired by Vincent Schwarzer on rumpkernel-users

don't -I imaginary opt directories

branches: 1.11.20; 1.11.38;
Reflect removal of fs_nfs.h and -DNFS

Globally define -Wno-pointer-sign, as it has become a pointless
exercise of "add it to every Makefile individually".

XXX: should autosynchronize with the rest of the kernel buildflags
in sys/conf/Makefile.kern.inc.

branches: 1.9.4;
* make features match those of the nfs module just to have them in-sync
* remove stubs.c since all are now provided by rumpnet

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: 1.7.2;
revert stack protector change.

Ignore stack-protector, since with nfs_bio.c it gets its life force
drained out. Yes, this is a quick kludge, should rather fix
nfs_bio.c to be less silly.

nfs_boot calls some networking stack routines directly. Since rump
will not invoke nfs_boot in the foreseeable future, provide those
routines as stubs in case sockin is used instead of the real
networking stack.

Make libnfs compile.

Install rump libraries and utilities to the base system and remove the
private non-installed build infrastructure from sys/rump.

breakdown of commit:
* install relevant headers into /usr/include/rump
* build sys/rump/librump/rumpuser and sys/rump/librump/rumpkern
from src/lib and install as librumpuser and librump, respectively
+ this retains the ability to test a librump build with just the
kernel sources at hand
* move sys/rump/fs/lib/libukfs and sys/rump/fs/lib/libp2k to src/lib
for general consumption, they are not kernel-space dwellers anyway
* build and install sys/rump/fs/lib/lib$fs as librumpfs_$fs
* add chapter 3 manual pages for rump, rumpuser, ukfs and p2k
* build and install userspace kernel file system daemons if MKPUFFS=yes
is spexified
* retire fsconsole for now, it will make a comeback with an actually
implemented version shortly

branches: 1.2.2; 1.2.4; 1.2.8; 1.2.14; 1.2.30; 1.2.34; 1.2.36; 1.2.38; 1.2.40;
more bsd.own.mk inclusion

branches: 1.1.2;
Introduce RUMPs - Runnable Userspace Meta-Programs

/sys/rump contains programs which run unmodified kernel code in an
emulated userspace environment. The kernel environment is provided
by librump. Currently supported are a number of file systems,
which by using puffs integrate seamlessly into the system and
provide a similar user experience to if the code was running as
part of the kernel. Potential future rumpification targets include
for example parts of the networking stack and some device drivers.

This work was supported by Google Summer of Code 2007.