shiny/driver/internal/win32: use //go:uintptrescapes

Use //go:uintptrescapes for SendMessage and SendScreenMessage
to force its parameters to be stored on the heap.

Fixes golang/go#16341.

Change-Id: Idf12c75d0690a91f97448a6af42a048bdf7854a0
Reviewed-on: https://go-review.googlesource.com/24921
Reviewed-by: Nigel Tao <nigeltao@golang.org>
3 files changed