Memo lookup overly matchy

[scottsb]

When looking up the memo file, the library will replace any instance of "DBF" or "dbf" in the table file path, not just in the extension. This means that if the path has those strings elsewhere in the path, the memo file won't be located, as the overzealously modified path likely won't exist.

[gam6itko]

fixed in 193f6b3