fix #21838 fix #21910 change filename encoding in zip files

This is a proposed fix for http://musescore.org/en/node/21910 and http://musescore.org/en/node/21838 it's a bit invasive and I would like some feedback before merging. In particular, does it work as expected on Mac and Linux?

Basically, I rename all the zip classes to make sure that we are using them at runtime. 
I changed the encoding of the filename in the zip file to UTF-8.
Apparently, TextStream doesn't care about the codec if it's set before the device. I added setCodec after each setDevice in exportxml.cpp