preload.c: Add hooks for mq_send/receive/close

And start implementing a fakemq API for simulating mqueues in userspace.
Switching between fakes an no fakes is handled with the USE_FAKES
define.
Rename preload.c -> fakemq.c
Rename library: fakemqueue => fakemq
fakemq: switch to the fakes
fakemq: protect data with mutex