array_extend should pre-grow the array to avoid multiple regrows

[Matt Giuca]

In interpret.m, array_extend currently appends each element of the second array to the end of the first. If the second array is much bigger than the first, this will result in multiple regrows of the array.

It should call vector.ensure_capacity first, to grow the first array to the required length, then perform the appends.

[Matt Giuca (mgiuca)]

Fixed in trunk r895.