flate.Compress: simplify huffman node comparisons

Instead of comparing each field, nodes are now compared as 32-bit values where `freq` is in the most significant bits.

Author: gooncreeper

lib/std/compress/flate/Compress.zig

@@ -993,14 +993,15 @@ const huffman = struct {
  const max_leafs = 286;
  const max_nodes = max_leafs * 2;
 
- const Node = struct {
- freq: u16,
+ const Node = packed struct(u32) {
  depth: u16,
+ freq: u16,
 
  pub const Index = u16;
 
+ /// `freq` is more significant than `depth`
  pub fn smaller(a: Node, b: Node) bool {
- return if (a.freq != b.freq) a.freq < b.freq else a.depth < b.depth;
+ return @as(u32, @bitCast(a)) < @as(u32, @bitCast(b));
  }
  };