Commit message auto-extraction formats

Updating README, NEWS, and CHANGES files

SVN commit messages that generate auto-NEWS and auto-CHANGES extractions should be formatted like the following examples:

 NEWS: snmpd: I did something really cool to the agent
 CHANGES: snmptrapd: fixed something minor in snmptrapd
 NEWS: perl: PATCH: 123,456: Applied patches 123 and 456 to support perl6
 CHANGES: BUG: 13: Fixed bug 13 & secured the world at large against hackers
 NEWS: perl: PATCH: 123: from Robert: did something
 NEWS: perl: PATCH: 123: from "Robert Story": did something else

All entries marked CHANGES will go into the CHANGES file. All entries marked NEWS go into both the NEWS and CHANGES file. Any text before the formatting above will be ignored, as will any text on subsequent lines. So everything for a particular entry should go on a single line (which will be auto-line-wrapped).

The extraction script is actually fairly lenient but please try to stick to the formats shown. See the dist/extractnews file for nasty regexp details.

The second field is a token, used to group related entries together. This should preferably be chosen from the following list:

 snmpd
 snmptrapd
 snmplib
 apps
 snmpusm, snmpget, ...           # if it applies to just one
 building
 documentation
 perl
 mib2c
 Linux, Solaris, Win32, FreeBSD, OpenBSD, Etc
 misc

(although it can technically be anything). For O/S-specific entries, please ensure that the token starts with an upper-case letter. (And for non-O/S-specific entries, that it doesn't!)

The release maintainer will doubtless need to edit and re-classify these entries further, of course, but this mechanism provides a start for them.