[poppler] RFC: Enabling libcurl by default

[Albert Astals Cid]

It allows for you to do stuff like

pdfinfo https://okular.kde.org/stuff/forms-scribus.pdf

or

pdftotext http://www.pdf995.com/samples/pdf.pdf foo.txt



We've had that code for a while and it seems to work quite well so i would 
like to move to having it enabled by default if curl is found rather than 
disabled by default.

What do you think?

Cheers,
  Albert