configure: show PKG_CONFIG_PATH and CFLAGS in config.log

When the build wrapper repo scripts run configure they set a custom
PKG_CONFIG_PATH environment variable. Show the value of this in
config.log to make it easier to rerun configure with a tweaked version
of the same parameters. Also show CFLAGS if set, as it's likely to
break things.
configure: fix target triplet check for mingw targets

mingw32 and mingw64's recommended triplets are i686-pc-mingw32 /
x86_64-w64-mingw32, neither has mingw32 in the middle.
configure: disable cross compilation auto detection

This didn't work very well when cross compiling from Linux to Windows:
it tries to execute an .exe file, which succeeds if wine is installed.
As consequence it detects "no" as result.

In general this won't work if emulation for the target architecture is
available. Remove it.
configure: use cross toolchain if --target is given

If --enable-cross-compile is specified, passing
--target=i686-w64-mingw32 for example will check if
i686-w64-mingw32-gcc can be used. This is only done if the compiler
isn't specified via --cc or the CC environment variable.

The same is done for some other build tools, such as pkg-config.
(Only the C compiler will try to use a fallback in this case.)
configure: allow changing pkg-config binary with --pkg-config
windows support: remove _UWIN define

The _UWIN define causes the mingw headers not to declare deprecated (on
Windows) function names such as open and mkdir. But the code uses these. I
have no idea why this used to work (if it even did), but the original
reason why it was defined seems to have vanished.
configure: add __USE_MINGW_ANSI_STDIO on MinGW

This makes MinGW redirect certain stdio functions (such as the sprintf
family) from the MSVCRT libc to a standard compliant MinGW
implementation.

This fixes a crash in talloc.c when compiling mplayer with MinGW-w64.
The problem is most likely with talloc_vasprintf(), which calls
vsnprintf with a small buffer and checks its return value to find out
how much space the formatted string requires. Without this commit,
vsnprintf would always return -1, and then the code calls abort().
(lachs0r figured out this one.)
windows: fix format string attributes on MinGW

MinGW maps the "printf" format string archetype to the non-standard
MSVCRT functions, even if __USE_MINGW_ANSI_STDIO is defined and set
to 1. We need to use "gnu_printf" to use the format strings as provided
by vsnprintf and similar functions to get correct warnings.

Since "gnu_printf" isn't necessarily available on other GCC compatible
compilers (such as clang), do this only on MinGW.
cleanup: Silence compilation warnings on MinGW-w64

Some of the code, especially the dshow and windows codec loader parts,
are extremely hacky and likely full of bugs. The goal is merely getting
rid of warnings that could obscure more important warnings and actual
bugs, instead of fixing actual problems. This reduces the number of
warnings from over 500 to almost the same as when compiling on Linux.

Note that many problems stem from using the ancient wine-derived
windows headers. There are some differences to the "proper" windows
header. Changing the code to compile with the proper headers would be
too much trouble, and it still has to work on Unix.

Some of the changes might actually break compilation on legacy MinGW,
but we don't support that anymore. Always use MinGW-w64, even when
compiling to 32 bit.

Fixes some warnings in the win32 loader code on Linux too.
windows support: unicode filenames

Windows uses a legacy codepage for char* / runtime functions accepting
char *. Using UTF-8 as the codepage with setlocale() is explicitly
forbidden.

Work this around by overriding the MSVCRT functions with wrapper
macros, that assume UTF-8 and use "proper" API calls like _wopen etc.
to deal with unicode filenames. All code that uses standard functions
that take or return filenames must now include osdep/io.h. stat()
can't be overridden, because MinGW-w64 itself defines "stat" as a
macro. Change code to use use mp_stat() instead.

This is not perfectly clean, but still somewhat sane, and much better
than littering the rest of the mplayer code with MinGW specific hacks.
It's also a bit fragile, but that's actually little different from the
previous situation. Also, MinGW is unlikely to ever include a nice way
of dealing with this.
windows: terminal: unicode, --msgcolor, size change

Make mp_msg() support unicode output, --msgcolor and variable screen
sizes.

Patch reintegrated by wm4.
af: print audio filter chain in verbose mode

The string format used in print_fmt() is taken from init_audio_filters().
af: fix crash when trying to use volume controls with AC3 pass-through

Changing the volume when softvol is enabled or if the audio output driver
doesn't support volume controls causes insertion of the "volume" filter.
This fails with AC3. Since the filter wasn't removed after that, and the
filter chain was in a bogus state, random crashes occured past this
point.

Fix it by reinitializing the filter chain completely on failure. Volume
controls simply won't work. (This can't be fixed, because AC3 is a
compressed format, and would require additional decoding/encoding passes
in order to support arbitrary volume changes.)

This also affects balance controls.
core: remove old EDL mode (--edl option)

Remove the old EDL implementation that was activated with the --edl
option. It is mostly redundant and inferior compared to the newer
demux_edl support, though currently there's no support for using the
same EDL files with the new implementation and the mute functionality
of the old implementation is not supported. The main reason to remove
the old implementation at this point is that the mute functionality
would conflict with following audio volume handling changes, and
working on the old code would be a wasted effort in the long run as at
some point it would be removed anyway.

The --edlout functionality is kept for now, even though after this
commit there is no code that could directly read its output.
configure: disable live555 by default

Latest liblivemedia version disables APIs we need. The code still
exists in the library and the changelog says the old interface can be
enabled with "#define RTSPCLIENT_SYNCHRONOUS_INTERFACE". However, the
code on the library side is disabled by default too, and seems to be
disabled in distro packages, so defining that in the player does not
help (just delays the failure until link time). It's possible the
distro packages will be changed to enable this, but since dropping
live555 support is desirable anyway, change configure to disable
support by default at least for now.

The live555 code is the only part of the source that's in C++.
Including C headers in code compiled as C++ has caused issues at
times, so deleting this code would have a maintenance benefit.
Reportedly the rtsp support in Libav has improved, so there should
be less need for live555.
configure: fix --enable-static

Hack around shell programming breakage that made Libav check fail with
--enable-static.
vo_gl: improve 10-bit YUV->RGB conversion accuracy slightly

Modify the YUV->RGB conversion matrix to take into account the
difference between the same color value being x/255 in a 8-bit texture
and x*256/65535 in a 16-bit texture (actually things are stored as
x*4/65535 for 10-bit color, but that can be ignored here). This 0.4 %
difference in the shader float value could make shades of gray in
10-bit (or generally more than 8 bit) YUV produce RGB values with
green slightly higher than red/blue.
Merge remote-tracking branch 'origin/master'
Revert "configure: disable live555 by default"

This reverts commit 3f659fd1766c3ae649cbdac21485cda06d29ccb6.