Write a function named stretch that accepts as a parameter a reference to a vector of integers, and modifies it to be twice as large, replacing every integer with a pair of integers, each half the original.
If a number in the original vector is odd, then the first number in the new pair should be one higher than the second so that the sum equals the original number.
For example, if a variable named v refers to a vector storing the values {18, 7, 4, 24, 11}, the call of stretch(v); should change v to contain {9, 9, 4, 3, 2, 2, 12, 12, 6, 5}.
(The number 18 is stretched into the pair 9, 9, the number 7 is stretched into 4, 3, the number 4 is stretched into 2, 2, the number 24 is stretched into 12, 12, and 11 is stretched into 6, 5.)
