Add option to set random seed for deterministic behavior

Bump version to 1.6

lib/options.c

@@ -10,6 +10,8 @@ mazeoptions_t* mazemaker_options_new() {
     // set defaults
     memset(result->wall_color, 0, 3);
     memset(result->background_color, 0xff, 3);
+    result->seed = 0;
+    result->seed_set = false;
 
     return result;
 }
@@ -78,3 +80,7 @@ int mazemaker_options_set_background_color(mazeoptions_t* options, char const* c
     return stringToColor(color_desc, options->background_color);
 }
 
+void mazemaker_options_set_seed(mazeoptions_t* options, rand_seed_t seed) {
+    options->seed = seed;
+    options->seed_set = true;
+}