configure: Separate "ln" command line arguments

This is more compatible and not more complicated.
configure: Identify icc compiler with a less ambiguous pattern
vorbisdec: cosmetics: rename variable avccontext to avctx

This is consistent with the rest of libavcodec.
vorbisenc: cosmetics: rename variable avccontext to avctx

This is consistent with the rest of libavcodec.
libschroedinger: cosmetics: rename variable avccontext to avctx

This is consistent with the rest of libavcodec.
cmdutils: only use libavresample when it is enabled

avprobe and avserver use cmdutils and do not strictly require libavresample.
avconv: remove an unused variable
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