SAP IQ numeric functions corner case differences

The following discrepancies in return values of numeric functions are caused by SAP IQ's behaviour.

1. COT(0)
   • results in OutOfRange error in Teiid
   • returns NULL in SAP IQ
2. EXP(n) - for n < -15
   • result is 0 in Teiid
   • result is in SAP IQ
     • 0 for -15 > n >=-745
     • NULL for n<=-746