circuitpy_mpconfig: enable 3-arg pow() with CIRCUITPY_FULL_BUILD

This is needed for a port of python3's decimal.py module.

Author: jepler

py/circuitpy_mpconfig.h

@@ -185,6 +185,7 @@ typedef long mp_off_t;
 // Turning off FULL_BUILD removes some functionality to reduce flash size on tiny SAMD21s
 #define MICROPY_BUILTIN_METHOD_CHECK_SELF_ARG (CIRCUITPY_FULL_BUILD)
 #define MICROPY_CPYTHON_COMPAT                (CIRCUITPY_FULL_BUILD)
+#define MICROPY_PY_BUILTINS_POW3              (CIRCUITPY_FULL_BUILD)
 #define MICROPY_COMP_FSTRING_LITERAL          (MICROPY_CPYTHON_COMPAT)
 #define MICROPY_MODULE_WEAK_LINKS             (CIRCUITPY_FULL_BUILD)
 #define MICROPY_PY_ALL_SPECIAL_METHODS        (CIRCUITPY_FULL_BUILD)