include/queue: Turn queue into a simple FIFO

include/queue: Turn queue into a simple FIFO

The queue module contains functions for file queues and queues with
unique contents, which should be used into separate modules to keep
modules simple and avoid mistakes such as using functions for normal
queues on file-queues.

This commit removes functions for file and unique queues from the
queue module, turning queues into simple FIFO data structures.