In the Bloom filter optimization, hash all strings and blobs into the same

value, because we do not know if two different strings might compare equal
even if they have different byte sequences, due to collating functions.
Formerly, the hash of a string or blob was just its length.  This could
all be improved.  Fix for the issue reported by
[forum:/forumpost/0846211821|forum post 0846211821].

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