style: rename variables for consistency

* src/lalr.c: Use trans for transitions, and reds for reductions, as
elsewhere in the code.
* src/state.h: Comment changes.

src/state.h

@@ -112,7 +112,7 @@ typedef struct state state;
 
 typedef struct
 {
-  int num;
+  int num;            /** Size of destination STATES.  */
   state *states[1];
 } transitions;