Strange behavior in Windows

[hyrodium]

These tests should be fixed.

ImageClipboard.jl/test/runtests.jl

Lines 12 to 17 in df6f881

	# FIXME, windows..
	if Sys.iswindows()
	@test RGBA.(img) == img2
	else
	@test img == img2
	end

ImageClipboard.jl/test/runtests.jl

Lines 25 to 28 in df6f881

	# FIXME, windows..
	if !Sys.iswindows()
	@test img == img2
	end

The _powershell_copy and _powershell_paste methods uses [Windows.Forms.Clipboard]::GetImage and [System.Windows.Forms.Clipboard]::SetImage, but these functions can't deal with alpha channel correctly.
https://github.com/hyrodium/ImageClipboard.jl/blob/df6f881d635304ce925f2996ba5d736893bbae92/src/_powershell.jl