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/util/files.c

@@ -75,7 +75,6 @@ main(int argc, char *argv[])
     extern s_char *timestampfil;
     extern s_char *infodir;
     extern s_char *commfil;
-    extern s_char *datadir;
     s_char buf[255];
     s_char tbuf[512];
     s_char *filename;