Revert #225 to make Windows+SDL builds use the SDL device again

[grorp]

Fixes #246. (Doesn't have an effect on #239.)

This PR reverts #225 to make Windows+SDL builds use the SDL device again. Currently, they contain both the Windows device and the SDL device, but they always use the Windows device.

This PR is only intended as a temporary fix until #225 is redone correctly.

How to test

Compile Minetest with -DUSE_SDL2=TRUE on Windows. Verify that the "About" tab shows "Irrlicht device: SDL".

[numberZero]

irrlicht/source/Irrlicht/CMakeLists.txt

Lines 375 to 384 in 9954667

	if(WIN32)
	set(IRRDRVROBJ ${IRRDRVROBJ}
	CIrrDeviceWin32.cpp
	)
	if(ENABLE_OPENGL)
	set(IRRDRVROBJ ${IRRDRVROBJ}
	CWGLManager.cpp
	)
	endif()
	endif()

Wouldn’t just replacing WIN32 with DEVICE STREQUAL "WINDOWS" be enough?
Edit: okay, that would likely result in link-time errors due to:

irrlicht/source/Irrlicht/Irrlicht.cpp

Lines 63 to 66 in 9954667

	#ifdef _IRR_WINDOWS_API_
	if (params.DeviceType == EIDT_WIN32 || (!dev && params.DeviceType == EIDT_BEST))
	dev = new CIrrDeviceWin32(params);
	#endif