py: Fix msvc C++ compiler warnings with MP_OBJ_FUN_MAKE_SIG macro.

When obj.h is compiled as C++ code, the cl compiler emits a warning about
possibly unsafe mixing of size_t and bool types in the or operation in
MP_OBJ_FUN_MAKE_SIG.  Similarly there's an implicit narrowing integer
conversion in runtime.h.  This commit fixes this by being explicit.

py/obj.h

@@ -278,7 +278,7 @@ typedef struct _mp_rom_obj_t { mp_const_obj_t o; } mp_rom_obj_t;
 #define MP_DECLARE_CONST_FUN_OBJ_KW(obj_name) extern const mp_obj_fun_builtin_var_t obj_name
 
 #define MP_OBJ_FUN_ARGS_MAX (0xffff) // to set maximum value in n_args_max below
-#define MP_OBJ_FUN_MAKE_SIG(n_args_min, n_args_max, takes_kw) (((n_args_min) << 17) | ((n_args_max) << 1) | (takes_kw))
+#define MP_OBJ_FUN_MAKE_SIG(n_args_min, n_args_max, takes_kw) (((n_args_min) << 17) | ((n_args_max) << 1) | ((takes_kw) ? 1 : 0))
 
 #define MP_DEFINE_CONST_FUN_OBJ_0(obj_name, fun_name) \
     const mp_obj_fun_builtin_fixed_t obj_name = \

py/runtime.h

@@ -79,7 +79,7 @@ int mp_print_mp_int(const mp_print_t *print, mp_obj_t x, int base, int base_char
 
 void mp_arg_check_num_sig(size_t n_args, size_t n_kw, uint32_t sig);
 static inline void mp_arg_check_num(size_t n_args, size_t n_kw, size_t n_args_min, size_t n_args_max, bool takes_kw) {
-    mp_arg_check_num_sig(n_args, n_kw, MP_OBJ_FUN_MAKE_SIG(n_args_min, n_args_max, takes_kw));
+    mp_arg_check_num_sig(n_args, n_kw, (uint32_t)MP_OBJ_FUN_MAKE_SIG(n_args_min, n_args_max, takes_kw));
 }
 void mp_arg_parse_all(size_t n_pos, const mp_obj_t *pos, mp_map_t *kws, size_t n_allowed, const mp_arg_t *allowed, mp_arg_val_t *out_vals);
 void mp_arg_parse_all_kw_array(size_t n_pos, size_t n_kw, const mp_obj_t *args, size_t n_allowed, const mp_arg_t *allowed, mp_arg_val_t *out_vals);