Fixed fast_atan2 function and failing unittests

Fixed the fast_atan2 function by recalculating the table and changing some "workarounds" in the code. 
Error before change: 0.111° 
Error after the correction: 8.20E-5°
Also fixed the unittests qa_pll_carriertracking, qa_pll_refout, qa_pll_freqdet.
Change done by Denis Bederov (DL3OCK) and Philipp Aigner (OE2AIP)