Importing usr.bin/printenv

Replaces printenv from commands/env. No Minix-specific changes
needed.

Change-Id: I64e63c9d0ca94faadc71906cf78d18fed5905e90
Importing usr.bin/env

Replaces commands/env. No Minix-specific changes needed.

Change-Id: I1aefebe360962ae52241384c54f9466253d783c6