py: This time, real proper overflow checking of small int power.
Previous overflow test was inadequate.
diff --git a/py/smallint.h b/py/smallint.h
new file mode 100644
index 0000000..14234fa
--- /dev/null
+++ b/py/smallint.h
@@ -0,0 +1,5 @@
+// Functions for small integer arithmetic
+
+bool mp_small_int_mul_overflow(machine_int_t x, machine_int_t y);
+machine_int_t mp_small_int_modulo(machine_int_t dividend, machine_int_t divisor);
+machine_int_t mp_small_int_floor_divide(machine_int_t num, machine_int_t denom);