Blender Git Loki

Cleanup: improve navigation gizmo flag use

Flag check for V3D_LOCK_CAMERA used boolean style assignment to a char,
which worked with this flag but could fail if other flags are added
that use this convention in the future.

- Add static type checks for values so any change to DNA types
will need to be made in the navigation gizmo too.
- Move camera lock check from `rv3d` to `v3d`,
as this isn't stored in the region data.