Change conversion methods to take objects by values

[d-unsed]

The following methods should take self by value, because technically they return the same Ruby
objects converted to another Rust type.

• Object::to

  Object::to<T: Object>(&self) -> T

  changes to

  Object::convert_into<T: Object>(self) -> T

• Object::try_convert_to

  Object::try_convert_to<T: VerifiedObject>(&self) -> Result<T>

  changes to

  Object::try_convert_into<T: VerifiedObject>(self) -> Result<T>

• Object::to_any_object()

  Object::to_any_object(&self) -> AnyObject

  changes to

  Object::into_any_object(&self) -> AnyObject

For example:

let fixnum = some_object.try_convert_into::<Fixnum>();

some_object should be consumed by convert_into, because fixnum and some_object correspond to the same object in Ruby.

[danielpclark]

Just curious about the Object::try_convert_into<T: VerifiedObject>(self) -> Result<T> scenario. Would taking ownership be bad in this case when the type isn't what you try for the first time? If the result is an Err(Error) because it's a different type the ownership would already be consumed… right?

[CodesInChaos]

@danielpclark The usual workaround is returning the original value as part of the error.