Nope, there are no packages that depend on newer libxau6 uploaded yet.
But I wouldn't port it if it wasn't needed as a depend for other apps (libxi6, which depends on libx11 and libxau6 and so on and so on)

If I make libxau6 v. 1.0.6...maemo2 containing the old files, it'll satisfy build-deps for sources which depend on newer version. This may be veeery confusing

If I could tell make: use the version from /opt/meecolay/include for includes (when it's not full path, just like "#include <iostream>") and libs from /opt/meecolay/lib for linking.