doc: update CODING file with newest features.

Signed-off-by: Emmanuel Roullit <emmanuel.roullit@gmail.com>
doc: update default unix socket path in POD header.

Signed-off-by: Emmanuel Roullit <emmanuel.roullit@gmail.com>
libdabba-rpc: use define to point to /var/run.

Better use the _PATH_VARRUN define, in case some other distro uses some
other path.

Signed-off-by: Emmanuel Roullit <emmanuel.roullit@gmail.com>
deb: update changelog file for v0.4.

Signed-off-by: Emmanuel Roullit <emmanuel.roullit@gmail.com>