sis.h: Get rid of all uses of long long's.
* (close_port read_uart write_uart uarta_tx): Don't seg fault
when can't open pty's.
* exec.c: Add two new instructions: smul, and divscc.
* interf.c (flush_windows): New routine to flush the register
windows out to the stack just before returning to GDB. Makes
backtraces work much better.