hwf4 timer: alpha-rename ARM to ARMING

- sometimes we get a weird transient compile bug because ARM is defined
  as 1?
- I don't have time to track it down, just fixing the symptom for now
ivory hxstream: put fbo at end of encode

* both the haskell decode and the ivory decode, expect
  a frame to have its own start and end fbo.
* both the haskell encode and the ivory encode (this)
  do not put an fbo at a frame end.
* this bug caused it to appear to drop every other frame
  recieved by the CommsecServer from the vehicle
commsec encrypt: get rid of unnecessary intermediate value

* was reviewing the generated C and it looked funny. There's
  no need to copy the argument mavStream to the stack only to
  copy it into the pkg array right afterwards.
* maybe at one point copyToPkg had a less general type signature
  or something
flight GCS Receive task: wibbles

* none of these should make a difference
flight datalink: wibbles

* shouldn't make any difference
gcs.sh: bugfixes
bump mavlink submodule