use always 64-bit arithemtics

[christoph-cullmann]

long is only 32-bit on 32-bit systems and on 64-bit Windows ensure we have consistent behavior

[christoph-cullmann]

Follow up of

coin-or/CoinUtils#245

See coin-or/Cbc#690

@jjhforrest

[christoph-cullmann]

Missed the labs vs. llabs.

[christoph-cullmann]

Seems I messed up the gomory change, just the src/CglPreProcess/CglPreProcess.cpp is needed to fix the bug, the other locations just look as wrong for large numbers and the USE_CGL_RATIONAL==0 path with the

typedef struct {
  int numerator;
  int denominator;
} Rational;

looks strange for me.