py/objtype: Change type of enum-to-qstr table to uint16_t to save space.

Qstr values fit in 16-bits (and this fact is used elsewhere in the code) so
no need to use more than that for the large lookup tables.  The compiler
will anyway give a warning if the qstr values don't fit in 16 bits.  Saves
around 80 bytes of code space for Thumb2 archs.

py/objtype.c

@@ -334,7 +334,7 @@ mp_obj_t mp_obj_instance_make_new(const mp_obj_type_t *self, size_t n_args, size
     return MP_OBJ_FROM_PTR(o);
 }
 
-const qstr mp_unary_op_method_name[] = {
+const uint16_t mp_unary_op_method_name[] = {
     [MP_UNARY_OP_BOOL] = MP_QSTR___bool__,
     [MP_UNARY_OP_LEN] = MP_QSTR___len__,
     [MP_UNARY_OP_HASH] = MP_QSTR___hash__,
@@ -408,7 +408,7 @@ STATIC mp_obj_t instance_unary_op(mp_unary_op_t op, mp_obj_t self_in) {
     }
 }
 
-const qstr mp_binary_op_method_name[] = {
+const uint16_t mp_binary_op_method_name[] = {
     /*
     MP_BINARY_OP_OR,
     MP_BINARY_OP_XOR,

py/runtime.h

@@ -57,9 +57,9 @@ typedef struct _mp_arg_t {
     mp_arg_val_t defval;
 } mp_arg_t;
 
-// defined in objtype.c
-extern const qstr mp_unary_op_method_name[];
-extern const qstr mp_binary_op_method_name[];
+// Tables mapping operator enums to qstrs, defined in objtype.c
+extern const uint16_t mp_unary_op_method_name[];
+extern const uint16_t mp_binary_op_method_name[];
 
 void mp_init(void);
 void mp_deinit(void);