(e.g., a file containing something like `$x^2 + y^2 = z^2$') and
converts it to a PNG image with no unnecessary surrounding
whitespace. Useful when you want to include TeX stuff in webpages /
other documents.
This currently calls /usr/bin/convert, so we should add ImageMagick.
svn path=/nixpkgs/trunk/; revision=8269
1c65a5b328