Made some changes to the I/O stream library for memory streams.
There were a number of potential problems due to the possibility
of integer overflow.
Changed some integral types to the larger types size_t or ssize_t.
For example, the function mem_resize now takes the buffer size parameter
as a size_t.
Added a new function jas_stream_memopen2, which takes a
buffer size specified as a size_t instead of an int.
This can be used in jas_image_cmpt_create to avoid potential
overflow problems.

Added a new function jas_deprecated to warn about reliance on
deprecated library behavior.
 static int mem_read(jas_stream_obj_t *obj, char *buf, int cnt)
 {
	ssize_t n;
 	assert(cnt >= 0);
 	assert(buf);
 
	JAS_DBGLOG(100, ("mem_read(%p, %p, %d)\n", obj, buf, cnt));
	jas_stream_memobj_t *m = (jas_stream_memobj_t *)obj;
	n = m->len_ - m->pos_;
	cnt = JAS_MIN(n, cnt);
	memcpy(buf, &m->buf_[m->pos_], cnt);
	m->pos_ += cnt;
 	return cnt;
 }

 static int mem_read(jas_stream_obj_t *obj, char *buf, int cnt)
 {
	int n;
 	assert(cnt >= 0);
 	assert(buf);
 
	JAS_DBGLOG(100, ("mem_read(%p, %p, %d)\n", obj, buf, cnt));
	jas_stream_memobj_t *m = (jas_stream_memobj_t *)obj;
	n = m->len_ - m->pos_;
	cnt = JAS_MIN(n, cnt);
	memcpy(buf, &m->buf_[m->pos_], cnt);
	m->pos_ += cnt;
 	return cnt;
 }
