The detection is rather sloppy, the bugdoc gets erroneously detected as
dBASE because it starts with '0', has a not-too-large header size at offset 4,
and a '\r' at a 32-byte alignment towards the start of the the not-too-large
header.

Add a plausibility check for the number of records in the file, which
helps for this bugdoc.

Change-Id: I466dfae18aa32fd62b79b9f524f22bea719721be