Add Cursor->find() TTL support

due to 
https://github.com/bcosca/fatfree/commit/85d4582624199c73d071e1bf70e5ab51117904ae

initiated 
https://groups.google.com/d/msg/f3-framework/U0SGFqNTeBM/4vFm5Uq8ZpcJ
Merge pull request #488 from emanwebdev/patch-5

Add Cursor->find() TTL support