Pam conversation function changes:

Pam conversation function changes:
 o use PAM_BUF_ERR as the return value when calloc() fails.
 o sanity check the value of num_msg
 o remove the workaround for old Apple PAM
 o PAM_AUTH_ERR is not a valid PAM conversation function return value

If getpass_error is set after a call to pam_verify (usually because
the user pressed ^C), return AUTH_INTR immediately instead of
checking the pam_verify return value.