[tex-live] texmf-dist -> texmf for TL'13

[Karl Berry]

It is not a mistake.  I liked Markus's suggestion of texmf-dist because
"texmf-dist" can refer to "distribution stuff" (ie, what we distribute),
just as "texmf-var" refers to "variable stuff", "texmf-local" means
"local stuff", etc.  It has a certain symmetry, where just plain "texmf"
inevitably can mean anything.  Sorry, I know you preferred "texmf", but
that was my thinking.

So, after some more internal discussion where no one had any strong
preference or other reasoning one way or the other, I suggested to Peter
B that he could change the Build system, and as usual, he was
super-efficient in doing so :).

Master/tlnet will not change in this regard, or many others, until TL'12
is frozen forever and we start pretests for TL'13.  Which will be later
this spring, not real soon.

k