devel/ode: fix and optionize building demos, other minor improvements

- Optionize building demos
- Fix depends (only depend on GL for demos, fix configure dependency
  detection by using USES=localbase and pkgconfig)
- Fix build of demo code (use older compatible C++ standard and
  patch some bits)
- Use native OPTIONS feature to make options mutually exclusive

PR:		254898
Approved by:	acm (maintainer)