options: make --no-... options work for OPT_REPLACED too

Do this by automatically adding the option, if the aliased option name
also has a "no-..." variant.

Could be easier by manually adding "no-..." variants to the option list,
but this seems better because you can't just forget it.
demux: don't always make --cache-secs override --demuxer-readahead-secs

It's confusing. Whether the new behavior is less confusing... whatever.
command: add properties for current bitrate

Fixes #1192.
DOCS/crosscompile-mingw: update

Unrecommend mingw-w64-cmake, point out MXE host requirements.