Implement exponential operator (**) to GDScript/Expressions

[Chaosus]

Added a support for pow operator to GDScript and Expressions:

Closes godotengine/godot-proposals#1045
Closes godotengine/godot-proposals#1580

[Mickeon]

Aah, I wish ^ wasn't reserved for the Bitwise XOR in GDScript, too. It would've been a nice opportunity to make it closer to the mathematical symbol, but I do digress.

Because of Python's influence, would it mean that, should this PR get merged, the Floor Division operator would be added, as well?

[Chaosus]

Because of Python's influence, would it mean that, should this PR get merged, the Floor Division operator would be added, as well?

Well, if the community have an interest in it - then why not? But as a proposal its better to be shown on the godotengine/godot-proposals first.

[Mickeon]

Never mind about the Floor Division proposal. As a point of reference, it didn't go so well last time.

[Chaosus]

Never mind about the Floor Division proposal. As a point of reference, godotengine/godot-proposals#1866.

Ah, I see. Than maybe it may be a source of confusion and not so needed for games as for the python developers.

[reduz]

Variant already provides the pow() function as builtin method. I would not add this to Variant as its more bloat. It can be simply syntax sugar in Expression and GDScript that ends up calling pow() internally.

[Chaosus]

@reduz To be honest without adding it to Variant is much more "bloating" to do rather than otherwise.

[fire]

Agree with reduz that this addition duplicates the pow function and adds confusion.

[akien-mga]

Looks good to me, there's just a stray modules/gdnative that got re-added and should be removed.

[Chaosus]

@akien-mga Done, I've removed it!

[akien-mga]

Thanks!