while here:
- remove utf8/utf8_stream.h, now we only need utf8/utf8.h to include
- add some new methods for converting from a utf8 stream to wide stream/string
- do some improvements in TextStream:
- don't use temporary objects to convert utf8/wide
- add put_stream() which takes TextStreamBase<> as its argument
(uses an iterator instead of get_char() for reading)
- let operator<<(const Space & space) serialize to json and not to Space
Those methods return true if the val character was escaped and put
to the out stream. If the character is invalid for such a stream
they only return true without putting it to the stream.
A wide string was first changed to utf-8 and then escaped to json/xml/csv
which is incorrect. First should be escaped and then changed to utf-8.
Add TextStreamBase<>::iterator and TextStreamBase<>::const_interator as classes
with a method wchar_t get_unicode_and_advance(const iterator & end)
to return one character either from utf-8 stream or from wide stream.
Let TextStreamBase<>::operator<<(wchar_t v) correctly use utf-8.