Declare all configuration variables in optlist.h. Include that

instead of declaring them all over the place.  This uncovered type
errors:
(s_p_etu, adj_update): Defined long, sometimes declared int.  Kills
big endian machines where sizeof(long) != sizeof(int).  Change to
int.

(set_option, delete_option, optstrset, intset, floatset, doubleset,
longset, optionset, optiondel, worldxset): Change linkage to static.

src/lib/commands/powe.c

@@ -229,7 +229,6 @@ out5(double value, int round_val, int round_flag)
 static void
 gen_power(void)
 {
-    extern double powe_cost;
     float *f_ptr;
     float *f_pt2;
     register struct powstr *pow;