since I'm going to update debian matplotlib pkg to 0.98.5 I'd like to
know how much dvipng lib is needed to let matplotlib work.
This is because adding a strong dependency on it (so that it's
installed everytime you install mpl) will take in even texlive, and
all its dependency, amounting in more than 200mb of space (an issue
presents even in ubuntu).
If dvipng (+texlive) is only needed for some "not-so-common"
situations (for example only to print complex math expression) then we
can move it to a wicker dependency, so that it's installed only if
expressly requested by the user (we'll inform users about this
Thanks for the attention,