Blender Git Loki

This fixes a Buffer Overflow Vulnerability reported by
Secunia Research

SAID: SA29818 (http://secunia.com/advisories/29818/)
Credit: Stefan Cornelius, Secunia Research

The old code trys to do a sscanf %s %d %s %d from a line in the
image file.

Now it copies over that line to a max buffer of size 540 chars before doing
the sscanf.
(I just picked a constant that was siginficatly large)

It also checks to see if it gets all 4 values if not return NULL.

Kent