found records. This makes resulting db for small capability databases
much smaller - for vgrind(1), the resulting vgrindefs.db is about 24KB
instead of ~500KB.
The hint passed to dbopen() is number of records in input files
rounded up to nearest power-of-two value and multiplied by two.
Besides being a nice conservative value, termcap.db become about
70KB bigger if the hint matches the count of records (1023), probably
due to hash overflows.
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