cmdutils: Only do the windows-specific commandline parsing on _WIN32

Fixes commandline parsing on Cygwin (on 64 bit, and on very recent
32 bit), where the configure check does find the CommandLineToArgvW
function (since it exists in the link libraries and in the headers),
but whose GetCommandLineW() only returns the application's path.
(This is due to a cygwin internal optimization, see
http://cygwin.com/ml/cygwin/2013-07/msg00538.html for details.)
Arguments are only given through main's argc/argv, and they're already
UTF-8.

Signed-off-by: Martin Storsjö <martin@martin.st>
libavutil: Don't use fcntl if the function does not exist

Not all platforms have the function.

Signed-off-by: Derek Buitenhuis <derek.buitenhuis@gmail.com>
Signed-off-by: Martin Storsjö <martin@martin.st>
avio: Add const qualifiers to ffio_read_indirect

This provides at least some protection against potential accidental
corruption of AVIO buffer workspace.

Signed-off-by: Martin Storsjö <martin@martin.st>
Voxware MetaSound decoder
h264_parser: Initialize the h264dsp context in the parser as well

Each AVStream struct for an H.264 elementary stream actually has two
copies of the H264DSPContext struct (and in fact all the other members
of H264Context as well):

((H264Context *) ((AVStream *)st)->codec->priv_data)->h264dsp
((H264Context *) ((AVStream *)st)->parser->priv_data)->h264dsp

but only the first of these was actually being initialised. This
prevented the addition of platform-specific implementations of
parser-related functions.

Signed-off-by: Martin Storsjö <martin@martin.st>
h264dsp: Factorize code into a new function, h264_find_start_code_candidate

This performs the start code search which was previously part of
h264_find_frame_end() - the most CPU intensive part of the function.

By itself, this results in a performance regression:
              Before          After
              Mean   StdDev   Mean   StdDev  Change
Overall time  2925.6 26.2     3068.5 31.7    -4.7%

but this can more than be made up for by platform-optimised
implementations of the function.

Signed-off-by: Martin Storsjö <martin@martin.st>
arm: Add assembly version of h264_find_start_code_candidate

               Before          After
               Mean   StdDev   Mean   StdDev  Change
This function   508.8 23.4      185.4  9.0    +174.4%
Overall        3068.5 31.7     2752.1 29.4     +11.5%

In combination with the preceding patch:
                Before          After
                Mean   StdDev   Mean   StdDev  Change
Overall         2925.6 26.2     2752.1 29.4     +6.3%

Signed-off-by: Martin Storsjö <martin@martin.st>
file: Move win32 utf8->wchar open wrapper to libavutil

When libavformat was changed to use the new avpriv_open function
in 51eb213d001, this silently bypassed the existing wrapper for
win32. Move the win32 wrapper into libavutil/file.c to make sure
it gets called everywhere (not just in the libavformat case).

This makes sure that non-ascii file names gets opened properly
(where file names internally are stored as utf8, but they get
converted to wchar_t and opened with _wsopen).

Signed-off-by: Martin Storsjö <martin@martin.st>
FATE: add a TAK test