some coding conventions:
- headers in include/core_api shall not include headers from other YafRay include dirs.
- headers in include/core_api shall not use HAVE_* options (like '#if HAVE_EXR')
- plugins using headers other than core_api ones need to have all libs added to their build environment for all HAVE_* options they pull in (directly or indirectly!)
- interface functions shall not have arguments or return types which depend on configurable typedefines (such as float, PLOAT and float)
- use doxygen comments to document non-obvious types, classes, interfaces and functions and their usage.
- use tabs, not spaces
- recommended tab width is 4
- 80 character terminals are from last century... everyone should be able to view at least 120 character long lines