Drop unused probing code from GST MediaParser

This completes what 8e986fb9 started (that commit set probe size
to zero, effectively disabling it but without dropping the code).

As a side effect, it fixes a warning reporting that the dropped
code was indeed not running.

Obsoletes patch #8165
Keep dropping unused code. See 9d14acb4.
Add missing CODECID define for vaapi. Thanks chithead.
Fix translation macro errors.
Fix avcodec version in MediaHandlerFfmpeg::description()
Fix warning: suggest parentheses around comparison.
Update missing script.
Use uint64_t from boost namespace.