matroska.pl: Sort the generated struct field list

Newer versions of perl randomize the hash used for hashes every time
it's run; this makes the order of the fields be non-deterministic. Tack
a sort there to make it deterministic. Needed to fix (or allow fixing) a
buggy gcc warning.
demux_mkv: fix warning

Now that matroska.pl generates struct fields in deterministic order,
this should be the last time I change this.

(gcc and clang shouldn't warn about this line of code, but since they
do, we want to workaround and silence the warning anyway.)
demux: rename Windows symbols

There are some Microsoft Windows symbols which are traditionally used by
the mplayer core, because it used to be convenient (avi was the big
format, using binary windows decoders made sense...). So these symbols
have the exact same definition as the Windows one, and if mplayer is
compiled on Windows, the symbols from windows.h are used.

This broke recently just because some files were shuffled around, and
the symbols defined in ms_hdr.h collided with windows.h ones. Since we
don't have windows binary decoders anymore, there's not the slightest
reason our symbols should have the same names. Rename them to reduce the
risk for collision, and to fix the recent regression.

Drop WAVEFORMATEXTENSIBLE, because it's mostly unused. ao_dsound defines
its own version if the windows headers don't define it, and ao_wasapi is
not available on systems where this symbol is missing.

Also reindent ms_hdr.h.
ta: re-add MinGW cargo culting

Not really cargo cult, but an unexplainable, needless difference that
just exists to annoy us.

Fixes that gcc on MinGW treats format specifiers in MSVC mode. Just why?
Why?
x11: make window-scale use windowed size in fullscreen mode

This is a bit more intuitive, since before, the window size was just set
to something random when setting the window-scale property during
fullscreen.
w32: implement functionality required for window-scale

Same semantics with respect to fullscreen as x11.