Add `Builder::whitelist_function`; deprecate `Builder::whitelisted_function`

[fitzgen]

The CLI flag is --whitelist-function, so we should be consistent and remove the "ed" from the builder method.

• Rename Builder::whitelisted_function to Builder::whitelist_function
• Add Builder::whitelisted_function that delegates to whitelist_function
• Mark whitelisted_function as #[deprecated = "use whitelist_function instead"]

[highfive]

Hi! If you have any questions regarding this issue, feel free to make a comment here, or ask it in the #servo channel in IRC.

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[treiff]

@highfive: assign me

[highfive]

Hey @treiff! Thanks for your interest in working on this issue. It's now assigned to you!

[fitzgen]

@treiff if you run into any questions, don't hesitate to ping me :)