[Dvipng] sleeping --follow

[Benito van der Zander]

Hi,
reading the documentation you would think that you can use the --follow 
option to speed up a tex->png conversion,
because you can run latex and dvipng in parallel.
Unfortunately, it becomes much slower, because for most small documents 
latex runs in less than a second, but
dvipng sleeps for 1s, if the dvi-file is not complete.

So, I suggest that it does something like this:

1. for the first 16 ms, dvipng shouldn't sleep at all, but try to read 
continuously from the file

2. afterwards sleep for 1 ms, then for 4 ms, 9, 16, ... up to a maximum 
of 1024 ms

3. once a character has been read and processed, it should go back to 
step 1, if the file is still not complete.


Benito