Updating the Prim Ref page

[Max Murtazin]

Corrected. Description for "Disc negative truncated" still needed. Anyone?

w.

"This suite of primitives pad their matching n-fdisc.dat primitives out to the bounding rectangle, spanning from x = 1 to the minimal x value of the matching primitive. They are used to integrate circular elements into rectilinear elements."

Best I can do. Sounds a bit messy tho