Add DEVELOPER flag, set by default.

This is a bit messier than I'd like, but we want to clearly remove all
dev code (not just have it uncalled), so we remove fields and functions
altogether rather than stub them out.  This means we put #ifdefs in callers
in some places, but at least it's explicit.

We still run tests, but only a subset, and we run with NO_VALGRIND under
Travis to avoid increasing test times too much.

See-also: #176
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

common/crypto_sync.c

@@ -11,11 +11,14 @@
 
 bool sync_crypto_write(struct crypto_state *cs, int fd, const void *msg TAKES)
 {
+#if DEVELOPER
+	bool post_sabotage = false;
 	int type = fromwire_peektype(msg);
+#endif
 	u8 *enc = cryptomsg_encrypt_msg(NULL, cs, msg);
 	bool ret;
-	bool post_sabotage = false;
 
+#if DEVELOPER
 	switch (dev_disconnect(type)) {
 	case DEV_DISCONNECT_BEFORE:
 		dev_sabotage_fd(fd);
@@ -31,11 +34,14 @@ bool sync_crypto_write(struct crypto_state *cs, int fd, const void *msg TAKES)
 	case DEV_DISCONNECT_NORMAL:
 		break;
 	}
+#endif
 	ret = write_all(fd, enc, tal_len(enc));
 	tal_free(enc);
 
+#if DEVELOPER
 	if (post_sabotage)
 		dev_sabotage_fd(fd);
+#endif
 	return ret;
 }