Try to fix abs(long long) in MSVC by returning the negative value for the "undefined" abs(-MAX-1).

Cython/Utility/Builtins.c

@@ -240,8 +240,8 @@ static CYTHON_INLINE PY_LONG_LONG __Pyx_abs_longlong(PY_LONG_LONG x) {
     return (unsigned PY_LONG_LONG) llabs(x);
 #elif defined (_MSC_VER)
     // abs() is defined for long, but 64-bits type on MSVC is long long.
-    // Use MS-specific _abs64 instead.
-    return (unsigned PY_LONG_LONG) _abs64(x);
+    // Use MS-specific _abs64() instead, which returns the original (negative) value for abs(-MAX-1)
+    return _abs64(x);
 #elif defined (__GNUC__)
     // gcc or clang on 64 bit windows.
     return (unsigned PY_LONG_LONG) __builtin_llabs(x);