Blender Git Loki

We found out memory got fragmented a lot for creating speed vectors on
large scenes... this because it has to make 3 entire databases to find
the vertex-speed to previous and next frame. Even though most of the
prev/next database was freed, the parts I kept were spread all over
memory.

This commit copies from the prev/next database only the two screen aligned
speed vectors and stores that in temporal per-object structs. Even whilst
it takes more memory, it then can free the entire database, making space
for the next database to be built.
Tests reveiled it saves quite some... well, if you want to believe the
'virtual memory' total unix gives... :)