[Rd] Locating MiKTeX

[Gabor Grothendieck]

I came across this program to locate MiKTeX file:

http://docs.miktex.org/2.7/sdk/findfile_8cpp-example.html

If the exe of this were included with R then it seems it might
provide a reliable way to locate MiKTeX which we don't currently have
since AFAIK there is no adequate registry key for MiKTeX.
Since its a tiny program it would not substantially affect the
R download.

(There is also a perl version of the same program there although
it relies on certain perl packages which would also have to be
present complicating things.)