Bug#853420: gle-graphics: fix ftbfs with GCC-7

[Christian T. Steigies]

Hi,
On Wed, Oct 18, 2017 at 10:50:40PM +0200, Sl?vek Banko wrote:
> Tags: + patch
> 
> By chance, I encountered the same bug in another project.
> I attach a patch here as well.

Thanks for your patch, much easier than what I tried: I removed abs() from
f2c.h and included cmath and using std:abs to the cpp files. Also I had to
do this in two files: fcontour.cpp and ffitcontour.cpp to get it to compile.
Your patch is less invasive, so I uploaded that now. If I could figure out
what happened to the upstream branch I would also push this to alioth...

thanks,
Christian