Avoid using abs with arbitrarily-sized ints.

Here the residue always fits into an int.  This fixes #1721.

Cython/Utility/TypeConversion.c

@@ -656,21 +656,21 @@ static CYTHON_INLINE PyObject* {{TO_PY_FUNCTION}}({{TYPE}} value, Py_ssize_t wid
         int digit_pos;
         switch (format_char) {
         case 'o':
-            digit_pos = abs(remaining % (8*8));
+            digit_pos = abs((int)(remaining % (8*8)));
             remaining = remaining / (8*8);
             dpos -= 2;
             *(uint16_t*)dpos = ((uint16_t*)DIGIT_PAIRS_8)[digit_pos]; /* copy 2 digits at a time */
             last_one_off = (digit_pos < 8);
             break;
         case 'd':
-            digit_pos = abs(remaining % (10*10));
+            digit_pos = abs((int)(remaining % (10*10)));
             remaining = remaining / (10*10);
             dpos -= 2;
             *(uint16_t*)dpos = ((uint16_t*)DIGIT_PAIRS_10)[digit_pos]; /* copy 2 digits at a time */
             last_one_off = (digit_pos < 10);
             break;
         case 'x':
-            *(--dpos) = hex_digits[abs(remaining % 16)];
+            *(--dpos) = hex_digits[abs((int)(remaining % 16))];
             remaining = remaining / 16;
             break;
         default: