oggenc: Set the right AVOption size for the pref_duration option

On big endian machines, the default value set via the faulty
AVOption ended up as 2^32 times too big.

This fixes the fate-lavf-ogg test which currently is broken on
big endian machines, broken since 3831362. Since that commit,
a final zero-sized packet is written to the ogg muxer in that test,
which caused different flushing behaviour on little and big endian
depending on whether the pref_duration option was handled as it
should or not.

CC: libav-stable@libav.org
Signed-off-by: Martin Storsjö <martin@martin.st>
adpcm: Avoid reading out of bounds in the IMA QT trellis encoder

This was broken in 095be4fb - samples+ch (for the previous
non-planar case) equals &samples_p[ch][0]. The confusion
probably stemmed from the IMA WAV case where it originally
was &samples[avctx->channels + ch], which was correctly
changed into &samples_p[ch][1].

CC: libav-stable@libav.org
Signed-off-by: Martin Storsjö <martin@martin.st>
configure: use .altmacro for gnu as check on arm

Clang's integrated assembler (after 3.4) does not yet support the
'.altmacro' directive which is only used in arm asm. Support is planned:
http://llvm.org/bugs/show_bug.cgi?id=18918
av_dict_set: fix potential memory leak with AV_DICT_DONT_OVERWRITE

av_dict_set leaks it key/value arguments if AV_DICT_DONT_OVERWRITE is
combined with AV_DICT_DONT_STRDUP_{KEY,VAL} and the key exists.