CharsetDetection: add checkStrForUtf8()
RegExp: add automatic UTF-8 mode based on given regular expression
Usage of RegExp: change from forced UTF-8 mode to new automatic UTF-8 mode
XBMCTinyXML: use new RegExp constructor
ScraperParser: add new attribute "utf8" for scraper RegExp, works similar attribute "cs", possible values "yes", "no", "auto" ("auto" by default)