r600g/sb: get rid of standard c++ streams

r600g/sb: get rid of standard c++ streams

Static initialization of internal libstdc++ data related to iostream
causes segfaults with some apps.

This patch replaces all uses of std::ostream and std::ostringstream in sb
with custom lightweight classes.

Prevents segfaults with ut2004demo and probably some other old apps.

Signed-off-by: Vadim Girlin <vadimgirlin@gmail.com>