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/buy.c

@@ -78,8 +78,6 @@ buy(void)
     time_t now;
     double tally;
     double canspend;
-    extern double buytax;
-    extern double tradetax;
     s_char buf[1024];
 
     if (!opt_MARKET) {
@@ -224,7 +222,6 @@ buy(void)
 int
 check_market(void)
 {
-    extern double buytax;
     struct comstr comm;
     struct sctstr *sect;
     struct ichrstr *ip;