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/gen/service.c

@@ -36,9 +36,9 @@
 #ifdef _WIN32
 #include <windows.h>
 
+#include "optlist.h"
 #include "prototypes.h"
 #include "service.h"
-#include "optlist.h"
 
 int
 install_service(char *program_name, char *service_name, char *config_file)