[tex-live] configure of dvipng is broken if libgd is not installed.

[Karl Berry]

    With the latest update of dvipng, its configure.ac demands that libgd
    is installed, instead of using the version we're building ourselves.

Yes, sorry.  I checked in the new version of dvipng yesterday (which I
shouldn't have done) but then didn't get to making it work with TL
again.  (Apparently all the support which Thomas wrote has been ignored
or they've never seen them.  Sigh.)

Dealing with this is my top priority for today.

    Right now I need to --without-dvipng to configure successfully.

Yeah, that's what I did too ...