This function computes the nearest integer value to val. Halfway cases are rounded to the larger in magnitude.

Examples:

 IloRound(IloInfinity) is IloInfinity.
 IloRound(-IloInfinity) is -IloInfinity.
 IloRound(0) is 0.
 IloRound(0.4) is 0.
 IloRound(-0.4) is 0.
 IloRound(0.5) is 1.
 IloRound(-0.5) is -1.
 IloRound(0.6) is 1.
 IloRound(-0.6) is -1.
 IloRound(1e300) is 1e300.
 IloRound(1.0000001e6) is 1e6.
 IloRound(1.0000005e6) is 1.000001e6.