make path matching in devfs rules consistent and sane (and safer)

Before this change path matching had the following features:
- for device nodes the patterns were matched against full path
- in the above case '/' in a path could be matched by a wildcard
- for directories and links only the last component was matched

So, for example, a pattern like 're*' could match the following entries:
- re0 device
- responder/u0 device
- zvol/recpool directory

Although it was possible to work around this behavior (once it was spotted
and understood), it was very confusing and contrary to documentation.

Now we always match a full path for all types of devfs entries (devices,
directories, links) and a '/' has to be matched explicitly.
This behavior follows the shell globbing rules.

This change is originally developed by Jaakko Heinonen.
Many thanks!

PR:		kern/122838
Submitted by:	jh
MFC after:	4 weeks
Style issue in r253661.

Pointed out by:	avg
MFC after:	1 month
fix UPDATING entry in r253677

MFC after:	3 weeks
X-MFC with:	r253677