[tex-live] TEXMFHOME when using install-tl on a Mac

[Mojca Miklavec]

I forgot to add: I already requested user-based Preference Pane once
(but even if Jérome didn't forget about that, it does require quite
some changes in basic architecture).

For "me" it would be useful for installing ConTeXt Distribution as
well, not just for MacTeX. Users don't need root privileges to install
ConTeXt, but installing Preference Pane requires them. (On the other
hand there are probably not so many users without root privileges on
Macs when compared to Linux.)

Mojca