Implement TODO in dlis_index_records
"handle situation where explicit bits are not the same for every segment"

Usecase:
File contains many LFs.
Last fdata in LF is not complete (expects successor).
Then FILE-HEADER follows, but it is assumed to be the part of the previous record (relevant to #222 as we do not check predecessor).
'Explicit' marker is overwritten to be as in the last record segment. So the fdata + fileheader were considered to be one "explicit" record.
Then find_fileheaders searches explicit records of type 0 (FHLR is 0), but because FDATA is also 0, 'combined' record was assumed to be the start of a new LF.

Which then caused issues while parsing the record as explicit, and debugging was not straightforward.