global: remove unnecessary includes from headers.

Each header should only include the other headers it needs to compile;
`devtools/reduce-includes.sh */*.h` does this.  The C files then need
additional includes if they don't compile.

And remove the entirely useless wire/onion_wire.h, which only serves to include wire/onion_wiregen.h.

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

devtools/mkcommit.c

@@ -23,6 +23,7 @@
 #include <common/htlc_wire.h>
 #include <common/key_derive.h>
 #include <common/status.h>
+#include <common/utils.h>
 #include <common/version.h>
 #include <inttypes.h>
 #include <stdio.h>