aarch64: assembler in clang-3.4 ignores the division by two

Values are positive powers of two, so just replace it with right shift.
build: handle library dependencies in configure

Instead of setting FFLIBS in each library Makefile configure
exports FFLIBS-$library in config.mak.
lavf: properly document the distinction between flags and ctx_flags
build: do not append $(FFLIBS-) to $(FFLIBS) if $(NAME) is not defined

Avoids including disabled library Makefiles.
lavc: add a native Opus decoder.

Initial implementation by Andrew D'Addesio <modchipv12@gmail.com> during
GSoC 2012.

Completion by Anton Khirnov <anton@khirnov.net>, sponsored by the
Mozilla Corporation.

Further contributions by:
Christophe Gisquet <christophe.gisquet@gmail.com>
Janne Grunau <janne-libav@jannau.net>
Luca Barbato <lu_zero@gentoo.org>
lavf: add AVFMT_FLAG_BITEXACT.

Use it instead of checking CODEC_FLAG_BITEXACT in the first stream's
codec context.

Using codec options inside lavf is fragile and can easily break when the
muxing codec context is not the encoding context.
lavf: drop the zero-sized packets hack

There should not be any valid reason anymore for passing completely
empty packets to lavf.
OTOH side data-only packets can be useful.
lavc: preserve the original private data in avcodec_copy_context()

If a non-NULL codec was passed to avcodec_alloc_context3(), private data
will be already allocated in dest.
lavc: properly handle subtitle_header in avcodec_copy_context()
build: add avresample after avcodec to FFLIBS

avcodec might depend on avresample and with --as-needed required symbols
might be get removed if avresample is linked before avcodec.
Fixes link failures of avprobe and avplay on aarch64 with
--enable-neon-clobber-test.
configure: fix enable-libopus help string
aarch64: opus NEON iMDCT and FFT

Opus celt decoding 11% faster and the iMDCT over 2.5 times faster on
Apple's A7.
FATE/opus: increase fuzz for the celt tests

This seems to be needed on some 32bit arches.
avisynth: set duration of audio streams

Signed-off-by: Anton Khirnov <anton@khirnov.net>
build: Support building using clang-usan and disable-optimization

Clang Undefined Behaviour Sanitizer seems to make non-constant constant
expressions, making the compilation fail when they are used within
inline assembly if no optimization is requested.

Add -O1 to the cflags to hide the misbehaviour.

Bug-Id: 683
hlsenc: Set the default codecs to AAC and H264

Most HLS implementation only support these codecs.

Signed-off-by: Martin Storsjö <martin@martin.st>
riff: Pass block_align to estimate frame duration

Fix incorrect wSamplesPerBlock(=0) written for ADPCM_IMA_WAV

Signed-off-by: Luca Barbato <lu_zero@gentoo.org>
dynamic loading of shared faac library
no Werror on implicit-function-declaration and missing-prototypes
custom icon and windows resource