- add new applet mkpasswd(1)

- add new applet mkpasswd(1)
function                                             old     new   delta
bb_ask                                                 -     355    +355
mkpasswd_main                                          -     296    +296
.rodata                                           121746  121847    +101
packed_usage                                       24632   24689     +57
static.methods                                         -      21     +21
gmatch                                               229     248     +19
bb_ask_stdin                                           -      11     +11
applet_names                                        1949    1958      +9
applet_main                                         1172    1176      +4
sulogin_main                                         503     505      +2
applet_nameofs                                       586     588      +2
sha256_hash                                          329     327      -2
correct_password                                     208     206      -2
parse_command                                       1442    1439      -3
get_cred_or_die                                      145     141      -4
passwd_main                                         1054    1044     -10
bb_askpass                                           348       -    -348
------------------------------------------------------------------------------
(add/remove: 4/1 grow/shrink: 7/5 up/down: 877/-369)          Total: 508 bytes