Fixes for r84057 LanguageTr uc/lc:

Fixes for r84057 LanguageTr uc/lc:
* Fixed inappropriate use of empty(), see style guide
* Made uc() and lc() respect the $first parameter. Not doing this completely broke the Turkish wikipedia, sending links like [[İngilizce]] to [[İngİlİzce]].
* Use str_replace() instead of preg_replace(). It's not necessary to use a unicode-aware replacement algorithm to do UTF-8 string replacements, due to details of the UTF-8 encoding format. I'm not sure how Hashar concluded that strtr() will produce garbage.