Force at most partial RELRO for rump_server and related libraries

rump_server with -l uses lazy resolution by default and thus cannot be
used with full RELRO/BIND_NOW.

Move rump kernel man pages from various sources to sys/rump

namely:
* src/lib is used only when building for POSIX'y platforms, but
the man pages have their use for all platforms
* rumpuser.3 is a function of the rump kernel, not one of the of
the POSIX'y implementation hosted in src/lib/librumpuser

no functional change

add man page for rumpfs

branches: 1.3.6; 1.3.12;
document rump_etfs

Back to WARNS=3 until the kernel source is -Wsign-compare friendly.

branches: 1.1.2;
Split vfs out of rumpkern into rumpvfs. Non-fs rumps no longer
include the file system code. File system rumps explicitly need
to include rumpvfs from now on.

Move rump kernel man pages from various sources to sys/rump

namely:
* src/lib is used only when building for POSIX'y platforms, but
the man pages have their use for all platforms
* rumpuser.3 is a function of the rump kernel, not one of the of
the POSIX'y implementation hosted in src/lib/librumpuser

no functional change

add RETURN VALUES

from Martin Lucina, via rumpkernel-users

Add rump_boot_etfs_register(), which can be used to specify etfs
nodes that will be available immediately when mountroot is done
and file systems are available.

The intended use is for example for firmware images to be available when
config_mountroot() hooks run.

branches: 1.6.2;
Note that etfs keys are not visible in directory listings,
per discussion with bad

branches: 1.5.4; 1.5.10;
fix prototype, document RUMP_ETFS_SIZE_ENDOFF

branches: 1.4.2;
Add some consistency dots though they make not much typographic sense; however,
just as much as in the other places in the enumeration.
Use Pa for a path.

Add missing .El
Maybe next we can have typoed comments break builds?

ahem, use public interface names in the doc

document rump_etfs

Move rump kernel man pages from various sources to sys/rump

namely:
* src/lib is used only when building for POSIX'y platforms, but
the man pages have their use for all platforms
* rumpuser.3 is a function of the rump kernel, not one of the of
the POSIX'y implementation hosted in src/lib/librumpuser

no functional change

branches: 1.2.4; 1.2.8;
Remove trailing whitespace.

add man page for rumpfs