Merge branch 'develop'

diff --cc src/prolog/machine/mod.rs
index ec9b11e7aa4a0fd372a6b26f60cc7b7c1898fe6e,bbc3e863e01b80fbc4fa8b59f67061c3eaed29a8..af3f0aec06ec437e9b30ac394836ffbeda2a008a
--- 1/src/prolog/machine/mod.rs
--- 2/src/prolog/machine/mod.rs
+++ b/src/prolog/machine/mod.rs
@@@ -138,7 -144,7 +144,7 @@@ impl Machine 
          compile_user_module(&mut wam, LISTS.as_bytes());
          compile_user_module(&mut wam, CONTROL.as_bytes());
          compile_user_module(&mut wam, QUEUES.as_bytes());
-       compile_user_module(&mut wam, NUMBERVARS.as_bytes());
 -        compile_user_module(&mut wam, NUMVARS.as_bytes());
++      compile_user_module(&mut wam, NUMVARS.as_bytes());
  
          wam
      }