Regex-based per op_ndn time/size limits

[Pierangelo Masarati <masarati@aero.polimi.it>]

Hi.

I just committed a small fix (after a nightmaring friday with people asking
for larger/smaller limits depending on their needs) that adds regex-based
per op_ndn time/size limits.
It is pretty simple and straightforward, but it seems to work fine.
At present it is exploited by back-ldbm only.

The configuration syntax is pretty simple. 


"limits"	[ "dn" [ "." { "exact" | "regex" } ] "=" ] <pattern> \
	<limit> [ <limit> [ ... ] ]

where <pattern> is a regex (default) or an exact dn, and <limit> is
"time=<value>" or "size=<value>"; future additional limits may be
added by simple extensions of the syntax.

An example:

limits	dn.exact="cn=Ando,ou=People,dc=example,dc=com" size=100
limits	dn=".*,ou=People,dc=example,dc=com" size=10 time=2
limits	".*" size=1 time=1

At present it MUST appear inside a database.  If need be, we can add
global op_ndn based limits as well.

In case only one limit is set, the otehr defaults to the global value,
which is also used in case no match is found.

Ando.