mem: Make av_strdup allocate using av_realloc

This makes sure that pointers from av_strdup are reallocable,
which is used in av_dict_set if the AV_DICT_APPEND flag is set.

Nothing should rely on pointers from av_strdup being aligned.

Signed-off-by: Martin Storsjö <martin@martin.st>
Merge remote-tracking branch 'qatar/master'

* qatar/master:
  mem: Make av_strdup allocate using av_realloc

Merged-by: Michael Niedermayer <michaelni@gmx.at>
avformat/hevcdec: cosmetics, whitespaces

This reduces the difference to the latest hevc demuxer

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
avformat/hevcdec: add more irap cases to hevc_probe()

This fixes fate-hevc-conformance-RAP_A_docomo_4

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>