Fixes uninitialized mhead

PFs later on when it tries to rwlock.
Fixes the VFS chmod

Permissions could not be removed, due to the |=.  We also can't just set
the mode directly, since the file type is squeezed into the top part of
the inode's mode.
chmod() and fchmod(), implemented with wstat (XCC)

Removes SYS_chmod, using SYS_wstat for it instead.  While I was at it,
wstat and fwstat work for 9ns completely.  For the VFS, it only supports
changing the mode.

Rebuild glibc.  Either copy over the two new files or just make clean.
If you chmod and get "invalid" or something similar, either you didn't
rebuild glibc properly or you didn't fill kfs again.