mil1553: add logic to manage versions

As a simplified version of git version management logic,
each binary here is compiled with a set of #define'd
symbols which the driver uses to store and display
its git commit.

Commits as per git describe --dirty and git show (SHA) are
stored, together with the original build directory
mil1553:lib: add (fake) locks to librti

rtilib_send_eqp and rtilib_recv_eqp are now
serialized by grabbing a lock in rtilib_lock_bc/rtilib_unlock_bc.
For the time being, these are noops.