[WIP pimpl] Removed ambiguous declarations for setter and other fixes.
[WIP pimpl] Removed ambiguous declarations for setter and other fixes.

- ambiguous declarations
- make from parameter of setter function const
- replaced ///// with /* ----- */ for C89 compliance

retuxx/tinyspline,msteinbeck/tinyspline,msteinbeck/tinyspline,msteinbeck/tinyspline,msteinbeck/tinyspline,msteinbeck/tinyspline,retuxx/tinyspline,retuxx/tinyspline,msteinbeck/tinyspline,msteinbeck/tinyspline,msteinbeck/tinyspline