CharsetConverter: add internal class CInnerConverter and move local static function to it
CharsetConverter: 'static' for all functions
CharsetConverter: define and implement class ConverterType
CharsetConverter: rewrote, use individual locks for each conversion type
CharsetConverter: use standard conversion for utf8ToSystem
CharsetConverter: add individual charset reset functions and reset charsets AFTER new settings are applied
CharsetConverter: do not skip last zero if original string have it at end
CharsetConverter: cleanup for iconv and refactoring for iconv_const
CharsetConverter: FriBiDi cleanup
CharsetConverter: Cleanup: remove 'using std'
Merge pull request #3326 from Karlson2k/charset_converter_rework_03

CharsetConverter rework - part 03