PR to cleanup/simplify build flags

[mcarans]

I've made a PR to clean up and simplify the build flags: https://github.com/OoliteProject/oolite/pull/523

Fix typo DOO_FOV_INFLIGHT_CONTROL_ENABLEDD

Remove FEATURE_REQUEST_5496 as no references in code

Replace OO_EXCLUDE_DEBUG_SUPPORT with NDEBUG in code for consistency - previously if you set NDEBUG (eg. BUILD_WITH_DEBUG_FUNCTIONALITY no) but not OO_EXCLUDE_DEBUG_SUPPORT, then compile failed.

Remove BUILD_WITH_DEBUG_FUNCTIONALITY as duplicates OO_EXCLUDE_DEBUG_SUPPORT (which equals NDEBUG). The simplification means that OO_EXCLUDE_DEBUG_SUPPORT effectively becomes a more human readable version of NDEBUG for use in config.make and using NDEBUG alone does not break builds.

Tested on Windows and Linux including building, installing and running package