elements: Global variable whether we are running on elements

Using a global variable is a bit lazy, but weaving the network type through
the entire stack is a daunting task. Maybe we can make that happen at a later
stage.

Most of the changes in `chainparams.c` are just formatting the
`genesis_blockhash` a bit nicer (`clang-format` to the rescue).

Signed-off-by: Christian Decker <decker.christian@gmail.com>

common/utils.h

@@ -10,6 +10,10 @@
 
 extern secp256k1_context *secp256k1_ctx;
 
+/* FIXME: Instead of using this as a global, we might want to pass it as
+ * context whenever we need it. The global var is just lazy... */
+extern bool is_elements;
+
 /* Allocate and fill in a hex-encoded string of this data. */
 char *tal_hexstr(const tal_t *ctx, const void *data, size_t len);