RFB_MAX_HEIGHT
howmany(RFB_MAX_HEIGHT, PIX_PER_CELL);
rc->crc_height = RFB_MAX_HEIGHT;
#define RFB_ZLIB_BUFSZ RFB_MAX_WIDTH*RFB_MAX_HEIGHT*4
howmany(RFB_MAX_HEIGHT, PIX_PER_CELL));