Add MSGTYPE config option

MSGTYPE allows the user to define how messages in the message
area behave. For example:

  MSGTYPE=stop "You swap places with "

would always make that message prompt for -more-.  Allowed types
are "show" (normal message), "hide" (do not show), "stop" (wait
for user), and "norep" (do not repeat message).

Adding this, because it's relatively simple, proven to work, and
it seemed to be the major thing betatesters felt was lacking when
compared to NAO.

src/decl.c

@@ -328,6 +328,8 @@ NEARDATA struct savefile_info sfrestinfo, sfsaveinfo = {
 #endif
 };
 
+struct plinemsg_type *plinemsg_types = NULL;
+
 #ifdef PANICTRACE
 char *ARGV0;
 #endif