Asks to keep RForm above (if set to true), so that it stays on top.
Note that you shouldn't assume the RForm is definitely above afterward, because other entities (e.g. the user or window manager) could not keep it above, and not all window managers support keeping windows above. But normally the window will end kept above. Just don't write code that crashes if not.
It's permitted to call this function before showing a window, in which case the window will be kept above when it appears onscreen initially.
Return value:
Returns true if the RForm is kept above other windows, false otherwise.