Add libuserdefs and use in cmd/{oamuser,passwd}

*** 317,326 ****
--- 317,328 ----
  file path=usr/lib/llib-lsip.ln
  file path=usr/lib/llib-lsldap
  file path=usr/lib/llib-lsldap.ln
  file path=usr/lib/llib-lsmbios
  file path=usr/lib/llib-lsmbios.ln
+ file path=usr/lib/llib-luserdefs
+ file path=usr/lib/llib-luserdefs.ln
  $(sparc_ONLY)file path=usr/lib/llib-lv12n
  $(sparc_ONLY)file path=usr/lib/llib-lv12n.ln
  file path=usr/lib/llib-lvolmgt
  file path=usr/lib/llib-lvolmgt.ln
  file path=usr/lib/llib-lwrap