memstat: add new recipe

memstat is a small proc-based utility designed to help the
system administrator figure out what's consuming memory.
Like ps, it lists all the processes, and how much private
memory each is using. Unlike ps, it also lists all the shared
objects (shared libraries and executables) that are in memory,
and which processes are using those shared objects.

Signed-off-by: Jackie Huang <jackie.huang@windriver.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>