(ITS#6083) ppolicy should also support invocation of an external password checker

[Guillaume.Rousse@inria.fr]

Full_Name: Guillaume Rousse
Version: 2.4.16
OS: Linux
URL: ftp://ftp.openldap.org/incoming/
Submission from: (NULL) (195.83.212.136)


Current implementation of ppolicy only accept an internal plugin as password
checker. However, writing native code is more difficult for many sysadmins than
using script languages. Moreover, it's also less safe, as any crash will
endanger the whole slapd process. Allowing to run an external process for
checking password would be desirable.