newbie in-game assistance with Guidebook notation

Provide some command assistance for newbies, but
suppress it with !cmdassist in the config file.

If someone misinterprets the Guidebook ^D, ^T
type command notation, this will pop up some
further information to possibly assist them and
explain the notation.

include/extern.h

@@ -1369,6 +1369,7 @@ E int NDECL(dowhatis);
 E int NDECL(doquickwhatis);
 E int NDECL(doidtrap);
 E int NDECL(dowhatdoes);
+E char *FDECL(dowhatdoes_core,(CHAR_P, char *));
 E int NDECL(dohelp);
 E int NDECL(dohistory);