sio_printf broken since newlib

[rickgaiser]

The old sio_printf function depends on vsnprintf from libc/newlib, making it too big to use for ELF's that need to be small. For this reason, sio_printf has been removed in a744144.

A more flexible solution would be to redirect the output of printf to different 'write' functions, to be called from here:

ps2sdk/ee/libc/src/ps2sdkapi.c

Lines 374 to 380 in 2120771

	int _write(int fd, const void *buf, size_t nbytes) {
	// HACK: stdout and strerr to serial
	//if ((fd==1) || (fd==2))
	// return sio_write((void *)buf, nbytes);
	return _ps2sdk_write(fd, buf, nbytes);
	}

An interface could look like:

libc_set_stdout(sio_write); // output redirected to EE SIO
libc_set_stdout(_ps2sdk_write); // output redirected to IOP (default)
libc_set_stdout(custom_stdout); // custom function that redirects to a file, or something else...

The idea is to give an application control over where the stdout will go to.