qemu-arm: Enable MICROPY_PY_ALL_SPECIAL_METHODS.

The qemu-arm port is for testing, so should have features enabled.

qemu-arm/mpconfigport.h

@@ -16,6 +16,7 @@
 #define MICROPY_LONGINT_IMPL        (MICROPY_LONGINT_IMPL_MPZ)
 #define MICROPY_FLOAT_IMPL          (MICROPY_FLOAT_IMPL_NONE)
 #define MICROPY_CAN_OVERRIDE_BUILTINS (1)
+#define MICROPY_PY_ALL_SPECIAL_METHODS (1)
 #define MICROPY_PY_ARRAY_SLICE_ASSIGN (1)
 #define MICROPY_PY_BUILTINS_FROZENSET (1)
 #define MICROPY_PY_BUILTINS_MEMORYVIEW (1)