PR# 19875 Memory leak in WEL

The following code:

p: EV_PIXEL_BUFFER

from until False loop
    p.destroy
    p.set_with_pointer (my_pointer)
end

will quickly run out of memory. This is due to a memory leak in WEL.

I figured out that the problem was due to a missing call to `destroy_item` in WEL_GDIP_IMAGE.load_image_from_stream (like we have in `load_image_from_file_original`).
You will find attached my modified version as well as an improvement to release external memory as soon as possible instead of waiting for the GC to call `dispose`.

Thanks you for this report and contribution.
We will check and test soon, and after a quick look at the difference, I think it is very likely to be integrated for next version.

Class WEL_COM_ISTREAM

Class WEL_GDIP_IMAGE