comment unused typedefs
remove unreachable break
miniz: remove MINIZ_NO_STDIO as it is uneeded since it is covered by catchall MINIZ_NO_ARCHIVE_APIS
agg_renderer: remove uneeded define of AGG_RENDERING_BUFFER row_ptr_cache<int8u> since it is already hardcoded in agg_renderer_buffer.h and agg_config.h
return human readable cairo error
fix a batch of unused variable warnings (leaving several with are true bugs/missing features)