Possible CLS improvement

[mnrvovrfc]

I was going to propose something with `_COPYIMAGE` but it has been iffy in one of my programs. Allocate `LONG` variable, create graphics screen and right afterward, use `_COPYIMAGE` to replicate it. Then use `_PUTIMAGE` to recall that handle.

`PCOPY` is a more elegant solution, though. Usually no more than two screens are needed, which on a 32-bit system would have gobbled a lot of RAM.