Inclusion of rtweekend.h still unclear

[whydoubt]

1.6.7 states "All main program files will include rtweekend.h first, so most other header files (where the bulk of our code will reside) can assume these definitions are already available."

I read that as: main.cc includes it up top, so we don't have to include it elsewhere. However, the source code is inconsistent with that premise, but the source code is also inconsistent with itself. Just looking at the other files mentioned in section 1.6.7 as needing changes:

• color.h, sphere.h, vec3.h in the src folder do NOT include rtweekend.h
• hittable.h, hittable_list.h in the src folder DO include rtweekend.h

Additionally, camera.h and material.h, which are introduced later, both include rtweekend.h in both the book and the src folder.

This effects of this carry over to the other books.