*Support for both v2 and v3 FRD header with appropriate reservation of
buffer space for different header sizes
*fake BU can generate data v2 and v3 FRD data
*EoR condition also when input run dir is missing
*valid fd check in input source should be >=0, not 1
*FRD version detection working now also for single-buffer mode in input source
more efficient method of micro-merging files
Merge pull request #4538 from smorovic/FRDHeaderFix

Frd header fix