Update Readme.md to use relative links

https://help.github.com/articles/relative-links-in-readmes
Merge pull request #45 from vBm/patch-1

Update Readme.md to use relative links
use the _countof macro when it makes sense to do so
libmpeg2.cpp: disable C4244 for x64
update Little CMS (git ff060c3)
update Changelog.txt
update VirtualDub to v1.10.4-test1
require Inno Setup v5.5.3
update Inno Setup Basque translation
lavr: fix mixing matrix reduction when normalization is disabled

In some cases when an input can contribute fully to the corresponding output, other inputs may also contribute to the same output. This is the case, for example, for the default 5.1 to stereo downmix matrix without normalization.