Close #3105

This should simplify the mms-bitfield issue and avoid the compilation of the dvdread plugin on Windows...

Otherwise, we'd use the maximum (5Mpixels) which is a bit large for
video purposes. Also, 5Mpixels exceeds the capacity of the XVideo
overlay.

This reverts commit 10b9d038.

Yeah, sorry guys, but it looks like the dxva2 code needs it :'(

modplug is a C++ library (including a C API). So we need the C++ linker,
at least when linking statically.

Signed-off-by: Pierre d'Herbemont <pdherbemont@free.fr>

This saves (from my test) more than 5 frames per seconds during live resize.

To convert from 4-bits to 8-bits channel, one should multiply by 17.
Acked-by: Antoine Cellerier <dionoea@videolan.org>

(not on some specific operating system)
Pointed-out-by: Ramiro Polla <ramiro.polla@gmail.com>

Don't force an explicit --disable-libva. This was especially silly on
non-libVA platforms.