configure: remove --datadir and other obsolete things

After OSD rendering was switched over to libass, nothing uses the
--datadir setting (font search in old code was last user). Remove the
switch. Also remove --enable-xshape (unused since internal GUI
removal) and some code remaining from ao_nas which was removed earlier.
build: clean up remnants from internal FFmpeg build

Clean up some obsolete configure tests and other things left over from
the time years ago when MPlayer used hacks to build FFmpeg inside the
same source tree.

Remove the configure switches --as, --ar, --ranlib. --ar and --ranlib
were useless since nothing is built as a library. --as wasn't directly
used; removing it means removing some sanity checks though (the
default assembler selected was tested to see that it could compile SSE
opcodes, which may be used in inline asm).

It's unlikely that anyone would try to make the filters depending on
Libavcodec internals build any more. Remove the undocumented configure
option --fmpeg-source-dir and remove the mcdeint and spp filters from
the source tree (they were already not built).

Remove some configure tests which were added for the sake of FFmpeg
build and whose results are not used by mplayer2 now.

Removing the memalign checks actually required removing two remaining
uses in the code. Also remove the malloc.h check and includes in code
(I guess the reason to add malloc.h includes at some point was
memalign use, though most of the files in question did not actually
use memalign now, if ever).
windows support: fix _wstat misusage

I have no idea when or how this broke, but _wstati64() is the function
we want anyway (64 bit filesize). Possibly this was a mingw-w64 bug.
It's unknown why "wstat()" just doesn't work in this case, as it's not
defined by MSDN and could be defined by mingw as it needs.
configure: change libcaca test to pkg-config
configure: go back to platform-based EXTERN_PREFIX test

Commit 6ad1f58ab8 (svn r28151) changed EXTERN_PREFIX detection to use
a "general" configure test instead of determining it based on
platform. However, this "general" test depends on assumptions about
object file contents, and actually fails if compiling with gcc -flto
for example. Go back to the simple platform-based test. Leave out the
OS2 (no longer supported) and OpenBSD !ELF (no idea what that is, but
probably not something I'd care about supporting) parts from the old
test.

Remove configure switch --nm, as it was only used for the hacky
EXTERN_PREFIX test.

Simply disable the use of EXTERN_ASM (same as EXTERN_PREFIX under
another name) in wrapper.S; this seems to have been added for OS/2
only, and the file should not get compiled on any platform with a
nonempty prefix now.
tv/radio: drop Video 4 Linux (V4L) version 1 support

The obsolete V4L1 has been removed from the Linux kernel already.
V4L2 is the current version.
stream_netstream: Remove netstream support

This allowed to move the input stream layer across the network,
allowing the user to play anything that mplayer could play remotely.
For example, playing a DVD related on a remote server (say, with the
host name "remotehost1") could be done by starting the netstream
server (from TOOLS/netstream.c) on that remote server, and then
running:

    mplayer mpst://remotehost1/dvd://

This would open the DVD on the remote host, and transfer the raw DVD
sector reads over network. It works the same for other protocols, and
all accesses to the stream layer are marshaled over network. It's
comparable to the way the cache layer (--cache) works.

It has questionable use and most likely was barely used at all.
There's lots of potential for breakage, because it doesn't translate
the stream CTRLs to network packets. Just get rid of it.
stream_cdda: support latest libcdio version
Merge remote-tracking branch 'upstream/master'

Conflicts:
	configure