Sync with upstream

Even though libgd/libgd#492 is not a relevant bug fix for PHP, since
the binding doesn't use the `gdImage*Ptr()` functions at all, we're
porting the fix to stay in sync here.
void init_source (j_decompress_ptr cinfo)
{
	my_src_ptr src = (my_src_ptr) cinfo->src;

	/* We reset the empty-input-file flag for each image,
	 * but we don't clear the input buffer.
	 * This is correct behavior for reading a series of images from one source.
	 */
	src->start_of_file = TRUE;
}

void init_source (j_decompress_ptr cinfo)
{
	my_src_ptr src = (my_src_ptr) cinfo->src;

	/* We reset the empty-input-file flag for each image,
	 * but we don't clear the input buffer.
	 * This is correct behavior for reading a series of images from one source.
	 */
	src->start_of_file = TRUE;
}
