Fix for Issue11475

[flashultra]

The following code ( for JS target) will return the value ("low: 4041473819") as max Int for JS is 9007199254740991 .
After the fix the value should be "low: -253493477"
The max value for Int32 should be 2,147,483,647

var i:Int64 = Int64.make(0xF0E3FF1B, 0x00000000);
var mcr:Int64 = Int64.ushr(i, 32);
trace("mcr: "+mcr);
trace("high: "+mcr.high);
trace("low: "+mcr.low);