function insertOneSpacing(v) {
  v = (v ^ (v << 8)) & 0x00ff00ff;
  v = (v ^ (v << 4)) & 0x0f0f0f0f;
  v = (v ^ (v << 2)) & 0x33333333;
  v = (v ^ (v << 1)) & 0x55555555;
  return v;
}
Inserts one 0 bit of spacing between a number's bits. This is the opposite of removeOneSpacing.

Example:
 input: 6
 input (binary):  110
 output (binary): 10100
                   ^ ^ (added)
 output: 20

@private
@param {number} v A 16-bit unsigned integer.
@returns {number} A 32-bit unsigned integer.
@see {@link https://fgiesen.wordpress.com/2009/12/13/decoding-morton-codes/}
@private