function builtin( x, start, end ) {
	return arraySlice.call( x, start, end );
}
Returns a shallow copy of a portion of an array using the `Array#slice` built-in.

@private
@param {Collection} x - input array
@param {integer} start - starting index (inclusive)
@param {integer} end - ending index (exclusive)
@returns {Array} output array

@example
var x = [ 1, 2, 3, 4 ];

var out = builtin( x, 1, 3 );
// returns [ 2, 3 ]