Field "layerm_vfs" of "struct layer_mount" got superseded by "mnt_lower".
Adapt consumers and remove the now unused field.

Ride 7.99.68

branches: 1.8.64; 1.8.68;
Create sysctl entries during module initialisation and destroy them
appropriately.

Many of these file systems are now ready for modularisation.

branches: 1.7.70; 1.7.74; 1.7.76; 1.7.78;
merge ktrace-lwp.

Remove __P()

branches: 1.5.12;
Tweak sysctl setup functions (the macros, actually) for use in lkms,
and tweak lkminit_*.c (where applicable) to call them, and to call
sysctl_teardown() when being unloaded.

This consists of (1) making setup functions not be static when being
compiled as lkms (change to sys/sysctl.h), (2) making prototypes
visible for the various setup functions in header files (changes to
various header files), and (3) making simple "load" and "unload"
functions in the actual lkminit stuff.

linux_sysctl.c also needs its root exposed (ie, made not static) for
this (when built as an lkm).

branches: 1.4.2;
Move UCB-licensed code from 4-clause to 3-clause licence.

Patches provided by Joel Baker in PR 22364, verified by myself.

branches: 1.3.22;
Typos and grammer fixes in comments (misc/13133 by Michael K. Sanders)

branches: 1.2.6; 1.2.8;
Fix doubled 'the's in comments.

Add overlay, a layered file system which overlays itself on
the underlying fs, rather than exporting it to another part of the
directory name space.