adduser/addgroup: support specifying uid/gid, add system
 account creation mode. By Tito.

function                                             old     new   delta
adduser_main                                         650     726     +76
addgroup_main                                        341     402     +61
addgroup_longopts                                      -      16     +16
adduser_longopts                                      97     103      +6
packed_usage                                       26161   26163      +2
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(add/remove: 1/0 grow/shrink: 4/0 up/down: 161/0)             Total: 161 bytes

4 files changed