don't allocate reserved UIDs/GIDs

[simonLeary42]

https://en.wikipedia.org/wiki/User_identifier

Debian Linux not only reserves the range 100–999 for dynamically allocated system users and groups, but also centrally and statically allocates users and groups in the range 60000-64999 and further reserves the range 65000–65533.[4]

[simonLeary42]

f6e979c

[simonLeary42]

#154