daemon: add global secp256k1 context for easy access.

This caches the tables, so you're not supposed to regenerate it all
the time.

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

daemon/lightningd.c

@@ -29,6 +29,8 @@ static struct lightningd_state *lightningd_state(void)
 
 	list_head_init(&state->peers);
 	timers_init(&state->timers, time_now());
+	state->secpctx = secp256k1_context_create(SECP256K1_CONTEXT_VERIFY
+						  | SECP256K1_CONTEXT_SIGN);
 	return state;
 }
 

daemon/lightningd.h

@@ -3,6 +3,7 @@
 #include "config.h"
 #include <ccan/list/list.h>
 #include <ccan/timer/timer.h>
+#include <secp256k1.h>
 #include <stdio.h>
 
 /* Here's where the global variables hide! */
@@ -21,5 +22,8 @@ struct lightningd_state {
 
 	/* Our peers. */
 	struct list_head peers;
+
+	/* Crypto tables for global use. */
+	secp256k1_context *secpctx;
 };
 #endif /* LIGHTNING_DAEMON_LIGHTNING_H */