Use pointer to const where possible

common/bolt11.c

@@ -235,7 +235,7 @@ static void decode_h(struct bolt11 *b11,
 static char *decode_x(struct bolt11 *b11,
                       struct hash_u5 *hu5,
                       u5 **data, size_t *data_len,
-                      size_t data_length, bool *have_x)
+                      size_t data_length, const bool *have_x)
 {
         if (*have_x)
                 return unknown_field(b11, hu5, data, data_len, 'x',
@@ -257,7 +257,7 @@ static char *decode_x(struct bolt11 *b11,
 static char *decode_c(struct bolt11 *b11,
                       struct hash_u5 *hu5,
                       u5 **data, size_t *data_len,
-                      size_t data_length, bool *have_c)
+                      size_t data_length, const bool *have_c)
 {
         u64 c;
         if (*have_c)