TYPO3 Core

For now, a locallang array is supposed to be in multiple charsets (one charset per lang) and is translated each time the label is requested. Of course it is very difficult to have a locallang.php in many charsets...

So xml locallang files were created, in only one charset. But locallang arrays are still expected to be in multiple Charsets ! So XML Locallang is converted to the expected charset, and on each usage of these labels, re-converted from this expected charset to the renderCharset (or the backend charset)

I think we can (or maybe we must ?) get rid of this old comportement, and save performances, memory, etd...

The idea is :
1) a php locallang file can declare its charset (as xml file does)
2) locallang arrays (from php file or xml file) will be converted into the renderCharset (maybe only the requested language, as in readLLXMLfile ?)
3) No other charset conversion is done in other functions (pi_getLL, getLL, getLLL, sL, ...)

Attached patch files are a way to make this work.
Please note that this system works : my pp_lib extensions (and all those wich depends on) uses it since some monthes and there's no known bugs.
(issue imported from #M6233)