tools/check-includes.sh: test that c files include their .h files.

This is best-practice (to ensure prototypes match up), but there were a
few places we didn't (at least, directly).  Make it a requirement,
either of form "foo.h" or <dir/foo.h>.

The noise is the change to our print templates.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

lightningd/json.c

@@ -18,6 +18,7 @@
 #include <common/utils.h>
 #include <gossipd/routing.h>
 #include <lightningd/chaintopology.h>
+#include <lightningd/json.h>
 #include <lightningd/jsonrpc.h>
 #include <lightningd/options.h>
 #include <sys/socket.h>