fate/gif: create meaningful gif encoding tests.
lavc/utils: merge side data after video encode.

This allows encoders to communicate side data to the muxers.
gif: use only one graphic control extension block per image.

The encoder now doesn't produce any extra graphic control extension
block anymore. Only the image is encoded, and the muxer writing
its own GCE containing notably the timing information now includes the
optional palette transmitted through packet side data.

This commit avoid setting clashes between the two GCE, and reduce the
size of the generated file with pal8 output.
lavf/gif: fix timing.

pkt->duration can not be used since the values are only based on frame
rate.
lavfi/afade: use AV_OPT_TYPE_DURATION

Signed-off-by: Paul B Mahol <onemda@gmail.com>
dynamic loading of shared faac library
avfilters: better behavior of frei0r on win32
programs: print version info and configuration only on -version
configure: fix modplug detection (it needs +lstdc++)
no Werror on implicit-function-declaration and missing-prototypes
configure: don't add -fPIC on MinGW-w64
custom icon and windows resource
use upstream version tag, my repo is always rebased