Test interaction of underscore literals and Cython length/sign suffixes.

tests/run/int_literals.pyx

@@ -23,6 +23,8 @@ def valid_underscore_literals():
     assert 1_00_00.5 == 10000.5
     assert 1e1_0 == 1e10
     assert .1_4 == .14
+    assert 1_0 == 1_0L == 1_0LL == 1_0UL == 1_0ULL
+    assert typeof(1_0ULL) == "unsigned long long"
 
 
 @cython.test_assert_path_exists(