Wrong mad_sat result

[mpflanzer]

The following kernel produces a wrong result with Oclgrind:

kernel void mad_sat_overflow(global long *res)
{
    res[0] = mad_sat(1L, -1L, 0L);
}

Output should be:

Argument 'res': 8 bytes
  res[0] = -1

but is:

Argument 'res': 8 bytes
  res[0] = -9223372036854775808