Fix Save/Resume error messages the same as Activity mode.
Add "Frame Time" (in ms) to extended F5 info; measures time per frame, the inverse of FPS, which is better for comparing performance.
Reworked RenderFrame's storage of primitives; they're now grouped by material, and rendered in groups, vastly reducing material switching needed. Not a significant performance improvement for me though.
git-svn-id: http://svn.uktrainsim.com/svn/openrails/trunk@182 a9f3cfff-6c41-7446-b0ca-052bd761e6eb