Move funding.[ch] to daemon/channel.[ch].

It's a more logical name, and a more logical place.  We change
"funding" to "channel" in the remaining exposed symbols, too.

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

commit_tx.h

@@ -1,7 +1,7 @@
 #ifndef LIGHTNING_COMMIT_TX_H
 #define LIGHTNING_COMMIT_TX_H
 #include "config.h"
-#include "funding.h"
+#include "daemon/channel.h"
 
 struct channel_state;
 struct sha256_double;