Buffer: Make Buffer::readFile() private.

Buffer: Make Buffer::readFile() private.

It's strange to have a public interface which has a function loadLyXFile and a function readFile. A user of this class will be confused about the difference.

Therefore, loadThisLyXFile will be next to loadLyXFile to stress that loadThisLyXFile will not load another file ;). I don't know whether all of you like that this function just calls readFile, but it feels good this way. All public paths for loading a file will now go through loadThisLyXFile (i.e. the paths that come from loadLyXFile), while readFile is a pure private function. If this doesn't make sense, just shout.

I think this improves the readability of the class.

git-svn-id: svn://svn.lyx.org/lyx/lyx-devel/trunk@35852 a592a061-630c-0410-9148-cb99ea01b6c8