Linux: minlen in pam_pwquality.so

The pam_pwquality module can be plugged into the password stack of a given service to provide some plug-in strength-checking for passwords. The code was originally based on pam_cracklib module and the module is backwards compatible with its options. - minlen: The minimum acceptable size for the new password (plus one if credits are not disabled which is the default). In addition to the number of characters in the new password, credit (of +1 in length) is given for each different kind of character (other, upper, lower and digit). The default for this parameter is 9. Note that there is a pair of length limits also in Cracklib, which is used for dictionary checking, a 'way too short' limit of 4 which is hard coded in and a build time defined limit (6) that will be checked without reference to minlen.