[tex-live] You should warn users not to install texlive 2008 if they have miktex installed

[Vasile Gaburici]

If Miktex is already installed Texlive's installer runs Miktex's
configuration programs instead of its own, and things go well after
that:
running mktexlsr C:/Program Files/texlive/2008/texmf-var
initexmf: This utility does not accept non-option arguments.
Etc.