Remove file name and line number output from witness(4)

Reduce code clutter by removing the file name and line number output
from witness(4). Typically it is easy enough to locate offending locks
using the stack traces that are shown in lock order conflict reports.
Tricky cases can be tracked using sysctl kern.witness.locktrace=1 .

This patch additionally removes the witness(4) wrapper for mutexes.
Now each mutex implementation has to invoke the WITNESS_*() macros
in order to utilize the checker.

Discussed with and OK dlg@, OK mpi@

Add a dedicated sysctl(2) node for witness(4).

The new node contains the subsystem's main control variable,
kern.witness.watch. It is aliased by the old name, kern.witnesswatch.
The alias will be removed in the future.

OK anton@ mpi@

Constipate all the struct lock_type's so they go into .rodata

ok visa@

Add kern.witnesswatch sysctl for controlling witness(4). By default,
lock order checking is disabled but it can be enabled at runtime.

Suggested by deraadt@ / mpi@
OK mpi@

Add a port of witness(4) lock validation tool from FreeBSD.

Go-ahead from kettenis@, guenther@, deraadt@

Add a dedicated sysctl(2) node for witness(4).

The new node contains the subsystem's main control variable,
kern.witness.watch. It is aliased by the old name, kern.witnesswatch.
The alias will be removed in the future.

OK anton@ mpi@

Constipate all the struct lock_type's so they go into .rodata

ok visa@

Add kern.witnesswatch sysctl for controlling witness(4). By default,
lock order checking is disabled but it can be enabled at runtime.

Suggested by deraadt@ / mpi@
OK mpi@

Add a port of witness(4) lock validation tool from FreeBSD.

Go-ahead from kettenis@, guenther@, deraadt@

Constipate all the struct lock_type's so they go into .rodata

ok visa@

Add kern.witnesswatch sysctl for controlling witness(4). By default,
lock order checking is disabled but it can be enabled at runtime.

Suggested by deraadt@ / mpi@
OK mpi@

Add a port of witness(4) lock validation tool from FreeBSD.

Go-ahead from kettenis@, guenther@, deraadt@