Added /proc/self resolution in open_inner(). When /proc/self
is opened, it resolves to /proc/<current-pid> by reading
context::current().pid and returning a ProcDir handle.
Cross-referenced with Linux 7.1 fs/proc/self.c proc_self_get_link()
which creates a symlink inode pointing to the current PID.
This enables 'ls /proc/self', 'cat /proc/self/status', and all
other tools that use /proc/self to access their own process info.
vasilito
6f7752892b