Warn users or provide auto-fix when `frame` is used in a sketch

[processing-bot]

Created by: benfry

In 4.0a2, removed the frame field in PApplet. It's been showing warnings to use surface since 2015, but we should provide a warning or even a way to auto-fix code that still uses it.

[processing-bot]

Created by: PoolloverNathan

Well, since Processing is already smart enough to know when I feel like there is an error somewhere and kindly turn off error detection, autofixing shouldn't be a problem.

[processing-bot]

Created by: urbanskimichal

Hello.
I created a pull request for this.
Is there a better option for me to link a pull request with an issue?

[processing-bot]

Created by: benfry

Thanks for the fix! Holding on this one pending how we decide to resolve #53