Fix id and groups for Macs.  Also make every util depend on common
common: remove extra cast
common: make get_group_list work for all users on Macs
common: fix for Linux
Begin using dependency info in the Makefile
id: remove warning about unused import
Merge pull request #268 from Arcterus/id-group-mac-fix

Fix id and groups for Macs.  Also add dependency information.