Remove all (incorrect) casts in abs(long long).

Cython/Utility/Builtins.c

@@ -235,20 +235,20 @@ static PyObject* __Pyx_Intern(PyObject* s) {
 
 static CYTHON_INLINE PY_LONG_LONG __Pyx_abs_longlong(PY_LONG_LONG x) {
 #if defined (__cplusplus) && __cplusplus >= 201103L
-    return (unsigned PY_LONG_LONG) std::abs(x);
+    return std::abs(x);
 #elif defined (__STDC_VERSION__) && __STDC_VERSION__ >= 199901L
-    return (unsigned PY_LONG_LONG) llabs(x);
+    return 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, 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);
+    return __builtin_llabs(x);
 #else
     if (sizeof(PY_LONG_LONG) <= sizeof(Py_ssize_t))
-        return (unsigned PY_LONG_LONG) __Pyx_sst_abs(x);
-    return (x<0) ? (unsigned PY_LONG_LONG)-x : (unsigned PY_LONG_LONG)x;
+        return __Pyx_sst_abs(x);
+    return (x<0) ? x*(PY_LONG_LONG)-1 : x;
 #endif
 }