Add a 'statement of intent' blurb to the top of MAINTAINERS. Split

the role of MAINTAINERS into advisory and strict parts. Introduce a
new LOCKS file to document enforced locked parts of the tree.

Strict locks are only added with core approval and will generally
have a renewal timeout.

Clarify that the source tree is a community effort, not a place to stake
out 'turf'.

This will be refined as needed.

With-core-hat-on:  Yes

LOCKS

@@ -0,0 +1,8 @@
+$FreeBSD$
+
+This file documents formal review/approval requirements that have been
+approved by core.
+
+subsystem       login   expires  notes
+--------------------------------------
+

MAINTAINERS

@@ -1,5 +1,23 @@
 $FreeBSD$
 
+Please note that the content of this file is strictly advisory.
+No locks listed here are valid.  The only strict review requirements
+are granted by core.  These are documented in src/LOCKS and enforced
+by CVSROOT/approvers.
+
+The source tree is a community effort.  However, some folks go to the
+trouble of looking after particular areas of the tree.  In return for
+their active caretaking of the code it is polite to coordinate changes
+with them.  This is a list of people who have expressed an interest in
+part of the code or listed their active caretaking role so that other
+committers can easily find somebody who is familiar with it.  The notes
+should specify if there is a 3rd party source tree involved or other
+things that should be kept in mind.
+
+However, this is not a 'big stick', it is an offer to help and a source
+of guidance.  It does not override the communal nature of the tree.
+It is not a registry of 'turf' or private property.
+
 subsystem	login	notes
 -----------------------------
 mergemaster	dougb	Prefers to pre-approve commits