Examples should be compilable

[kirtchev-adacore]

Currently, the FLS examples are just random snippets of code, usually illustrating a particular construct. Ideally, all FLS examples should be compilable stand-alone programs that are verified by a tool during building.

[tshepang]

this is not me blocking progress on this one, but just me expressing my current thinking

FLS is very inconsistent about examples, and they are not needed for qualification, so am not sure we should have them (or, at least, am not sure we should add new ones). Am a little sympathetic to the idea of having them when showing difficult parts of the rules, but am not exactly convinced.