Make Qt/Emb use another tmp directory

It would be nice if it was possible to make Qt/Emb use another directory than /tmp for window server communications [also fonts].

This will ease porting Qt/Emb but is also useful for customers that use Qt/Emb on a multi user system. Qt/Emb doesn't delete /tmp/qtembedded "for caching purposes". when the qws server shuts down. If a user then starts a new qws server then the user gets a file permissions error.

Also, all temporary files created should be user specific.