/* $DOC$
   $NAME$
      ft_GCD()
   $CATEGORY$
      Math
   $ONELINER$
      Calculate greatest common divisor of two numbers
   $SYNTAX$
      ft_GCD( <nNumber1>, <nNumber2> ) -> nGCD
   $ARGUMENTS$
      <nNumber1> is the first number to find the GCD of.

      <nNumber2> is the second number to find the GCD of.
   $RETURNS$
      The greatest common divisor of the 2 numbers, or 0 if either is 0.
   $DESCRIPTION$
      This function calculates the greatest common divisor between 2 numbers,
      i.e., the largest number that will divide into both numbers evenly.  It
      will return zero (0) if either number is zero.
   $EXAMPLES$
      ? ft_GCD( 10, 15 )                  // Result: 5
      ? ft_GCD( 108, 54 )                 // Result: 54
      ? ft_GCD( 102, 54 )                 // Result: 6
      ? ft_GCD( 111, 17 )                 // Result: 1
   $END$
 */