Break inclusion cycle: prototypes.h and commands.h included each

other.  Ensure headers in include/ can be included in any order
(except for econfig-spec.h, which is special).  New header types.h to
help avoid inclusion cycles.  Sort include directives.  Remove some
superflous includes.

src/lib/global/news.c

@@ -41,9 +41,7 @@
 
 #include <config.h>
 
-#include "misc.h"
 #include "news.h"
-#include "nsc.h"
 
 static char no_news[] = "does nothing in particular to %s";