Allow complex lengths for temp_array

[CareyJWilliams]

Recently I've found myself often wanting to temporarily copy arrays in ChoiceScript to do some changes without affecting the original array. It's a bit more awkward than it needs to be at the moment because temp_array doesn't accept a complex length. I understand why create_array doesn't, but I don't think this restriction is necessary for temp_array?

Usage

*create_array my_global_array 5 1 2 3 4 5
*temp_array my_local_array my_global_array_count 0
*comment you can now loop to copy safely

An alternative, more specific approach, might be a whole new command, something like:

*create_array my_global_array 5 1 2 3 4 5
*temp_array_clone my_local_array "my_global_array"
${my_local_array[3]} == 3

Cleaner but less flexible. Allowing temp_array to take complex values also opens up a lot of options for dynamic variable creation (combining multiple arrays etc).