Fix C compiler warning about implicit integer downsizing.

Closes #2194.

Cython/Utility/TypeConversion.c

@@ -678,8 +678,8 @@ static CYTHON_INLINE PyObject* {{TO_PY_FUNCTION}}({{TYPE}} value, Py_ssize_t wid
     // 'dpos' points to end of digits array + 1 initially to allow for pre-decrement looping
     char *dpos, *end = digits + sizeof({{TYPE}})*3+2;
     const char *hex_digits = DIGITS_HEX;
-    Py_ssize_t ulength;
-    int length, prepend_sign, last_one_off;
+    Py_ssize_t length, ulength;
+    int prepend_sign, last_one_off;
     {{TYPE}} remaining;
     const {{TYPE}} neg_one = ({{TYPE}}) -1, const_zero = ({{TYPE}}) 0;
     const int is_unsigned = neg_one > const_zero;
@@ -743,7 +743,7 @@ static CYTHON_INLINE PyObject* {{TO_PY_FUNCTION}}({{TYPE}} value, Py_ssize_t wid
     if (ulength == 1) {
         return PyUnicode_FromOrdinal(*dpos);
     }
-    return __Pyx_PyUnicode_BuildFromAscii(ulength, dpos, length, prepend_sign, padding_char);
+    return __Pyx_PyUnicode_BuildFromAscii(ulength, dpos, (int) length, prepend_sign, padding_char);
 }