Parameters following Include line dropped

[wahn]

The current parser drops parameters following an Include line, e.g.:

> pwd
/mill3d/users/jan/Graphics/Rendering/PBRT/pbrt-v3-scenes/cloud
> grep sigma_a f15-4c.pbrt -B 1
	Include "geometry/density_render.70.pbrt"
	  "color sigma_a" [10 10 10] "color sigma_s" [90 90 90]

The C++ parser reads values for sigma_a and sigma_s, but the Rust parser currently ignores those.

Lets fix that ...