Fixes finally behaviour

[Qqwy]

Fixes:

• Reraising from catch will now first run inner finally block before re-throwing to the outer environment.
• Debugging text is now hidden unless the DEBUG_EXCEPTIONAL flag is set.
• example.c contains a lot more examples of different cases of simple and complex try/catch/finally scenarios.
• Some superfluous statements have been refactored.
• Improved documentation.

[Qqwy]

I want to fix some compiler warnings before merging :-).

[Qqwy]

I believe these changes were merged a long time ago, albeit not through this PR