(ITS#5159) make slap_passwd_parse() non-destructive

[hyc@OpenLDAP.org]

Full_Name: Howard Chu
Version: HEAD/RE24
OS: 
URL: ftp://ftp.openldap.org/incoming/
Submission from: (NULL) (63.193.240.128)
Submitted by: hyc


In RE23 the slap_passwd_parse() function parses the exop data destructively, so
it cannot be successfully parsed again by any other function that needs to. In
HEAD there is a new LBER option to specify non-destructive parsing of strings,
and slap_passwd_parse() has been changed to use this option.