avconv: drop additional strerror fallback

strerror_r is called by av_strerror already.
avconv: report the error for codec open failure

External codec may have corner case reason to fail at init, better
report them instead having the user wonder.
ogg: relax demuxer conformance checks

Some samples in the wild are missing headers that are expected by the
specification but in practice do not affect decoding.
configure: More msvc/icl combining

Signed-off-by: Derek Buitenhuis <derek.buitenhuis@gmail.com>
configure: Simplify an expression with enabled_all.
configure: whitespace cosmetics
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