Default to aux_len=26

Layout now:
- 38 bits base hash
- 17 bits auxiliary hash
- 1 bit first_strobe_is_main flag
- 8 bits strobe2 offset
- 32 bits position
- 32 bits reference/contig index

src/cmdline.hpp

@@ -52,7 +52,7 @@ struct CommandLineOptions {
     int u { 7 };
     int s { 16 };
     int c { 8 };
-    int aux_len{24};
+    int aux_len{26};
 
     // Alignment
     int A { 2 };