A cleanup for MDEV-17249 MAKETIME(-1e50,0,0) returns a wrong result

Unary minus operation for the smallest possible signed long long value (LONLONG_MIN) is undefined in C++. Because of this, func_time.test failed on ppc64 buildbot machines. Fixing the code to avod using undefined operations. This is fix is similar to "MDEV-7973 bigint fail with gcc 5.0"

Author: abarkov

sql/sql_type_int.h

@@ -33,7 +33,11 @@ class Longlong_hybrid
  bool neg() const { return m_value < 0 && !m_unsigned; }
  ulonglong abs() const
  {
- return neg() ? (ulonglong) -m_value : (ulonglong) m_value;
+ if (m_unsigned)
+ return (ulonglong) m_value;
+ if (m_value == LONGLONG_MIN) // avoid undefined behavior
+ return ((ulonglong) LONGLONG_MAX) + 1;
+ return m_value < 0 ? -m_value : m_value;
  }
 };