* (bug 5477) Searches for words less than 4 characters now work without

* (bug 5477) Searches for words less than 4 characters now work without
  requiring customization of MySQL server settings

Short words are padded so they now get indexed. Yay!

Adapted part of Werdna's patch, with some additional cleanup:
* Using 'U00' to pad instead of 'SMALL' to reduce false positives (eg search for "small*" could match "Smallville" and "SMALLc")
* Checking server's ft_min_word_len variable to see if we need to do anything. This preserves index compatibility with existing installations which have customized their index length.
* Some further cleanup on redundant code -- just toss everything through lc() and be done with it :D
* Cleaned out some more evals in zh and yue classes :P
* Fixed yue class to call the parent adjustor properly