mpeg12: Ignore slice threading if hwaccel is active

Slice threading does not work with hardware acceleration, as decoding
is per-picture.  This fixes Bugzilla #542.

Signed-off-by: Diego Biurrun <diego@biurrun.de>
miscellaneous typo fixes
dynamic loading of shared faac library
no Werror on implicit-function-declaration and missing-prototypes
custom icon and windows resource
use upstream version tag, my repo is always rebased