Deprecation warnings for features we plan to remove

[cameel]

We decided to introduce deprecation warnings for the following features:

• Remove support for the catch all (*) in the using statement #11882
• Reconsider operators on ContractType #11700
• Remove abi.encodePacked #11593
• Remove .send and .transfer. #7455
• Remove ABIEncoderV1 #11323
• Disallow internal function pointers in storage #15794
• Drop support for --opcodes #14033

Some of them may be removed already in 0.9.0, for some that may be too soon, but we should start preparing the ground already to elicit some feedback and keep users aware.

[cameel]

@clonker suggests a warning for #14033 as well.

[cameel]

Regarding #14033, @ekpyron pointed out that we didn't think a deprecation warning was not necessary since there won't be much of a deprecation period until 0.9.0. Still, if we do add these warnings before 0.9.0, I think it should be included.