Eliminate a few unbraced statements that crept into the code.

Also avoids some easily avoided multiple-returns.

src/bench_ecdh.c

@@ -29,7 +29,9 @@ static void bench_ecdh_setup(void* arg) {
     };
 
     data->ctx = secp256k1_context_create(0);
-    for (i = 0; i < 32; i++) data->scalar[i] = i + 1;
+    for (i = 0; i < 32; i++) {
+        data->scalar[i] = i + 1;
+    }
     CHECK(secp256k1_ec_pubkey_parse(data->ctx, &data->point, point, sizeof(point)) == 1);
 }