Make unary minus and unary plus return int for byte and short

compiler/testData/codegen/boxWithStdlib/dataClasses/hashcode/byte.kt

@@ -1,7 +1,7 @@
 data class A(val a: Byte)
 
 fun box() : String {
-   val v1 = A(-10.toByte()).hashCode()
-   val v2 = (-10.toByte() as Byte?)!!.hashCode()
+   val v1 = A(10.toByte()).hashCode()
+   val v2 = (10.toByte() as Byte?)!!.hashCode()
    return if( v1 == v2 ) "OK" else "$v1 $v2"
 }