modify cBESSELI function

cell/model/FormulaObjects/engineeringFunctions.js

@@ -991,15 +991,13 @@
 		 if ( n < 0 ){
 			 return this.value = new cError( cErrorType.not_numeric );
 		 }
+		 if(x < 0){
+		 	x = Math.abs(x);
+		 }
+		 n = Math.floor(n);
+
 		 this.value = BesselI( x, n );
 		 return this.value;
-
-	 };
-	 cBESSELI.prototype.getInfo = function () {
-	 return {
-	 name:this.name,
-	 args:"( effect-rate , npery )"
-	 };
 	 };*/
 
 	/**