proc filesystem

This patch adds a simple Linux compatible procfs filesystem.  It
currently implements a "/proc/self/maps" file which is looked up by
OpenJDK during startup.

Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
vfs: mount procfs at boot

Add a '/proc' directory to OSv image and mount procfs on it.

Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
tests: miscs-procfs.so

Add a simple manual test case for checking "/proc/self/maps" output.

Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>