frame synchronization mechanism and robustification of if4p5 packet handling for out-of-order asynchronous reception (PDLFFT)

This hotfix does not change the processing at all.
At this point, stat_re == 0, so the behavior is the
same as before. But the code was wrong. There should
have been no test, it's a NACK, period.

pdcch is now filled with dummy data (like it used to be) to enable better estimation of signal energy (also in unitary sims and oaisim)