Fix wrong too small size of argument unfiltered_max

in ia64_coder_init(). It triggered assert() in
simple_coder.c, and could have caused a buffer overflow.

This error was probably a copypaste mistake, since most
of the simple filters use unfiltered_max = 4.

src/liblzma/simple/ia64.c

@@ -97,7 +97,7 @@ ia64_coder_init(lzma_next_coder *next, lzma_allocator *allocator,
 		const lzma_filter_info *filters, bool is_encoder)
 {
 	return lzma_simple_coder_init(next, allocator, filters,
-			&ia64_code, 0, 4, is_encoder);
+			&ia64_code, 0, 16, is_encoder);
 }