libpwdgrp/pwd_grp.c: allocate local storage on first call, not in bss. -1k bss

libpwdgrp/pwd_grp.c: allocate local storage on first call, not in bss. -1k bss

function                                             old     new   delta
get_S                                                  -      31     +31
bb_internal_getpwnam                                  38      44      +6
bb_internal_getgrnam                                  38      44      +6
bb_internal_getgrgid                                  38      44      +6
ptr_to_statics                                         -       4      +4
static.resultbuf                                      88       -     -88
static.buffer                                       1024       -   -1024
------------------------------------------------------------------------------
(add/remove: 2/2 grow/shrink: 3/0 up/down: 53/-1112)        Total: -1059 bytes