These are the relevant info BIPs.

NODE_GETUTXO
https://github.com/bitcoin/bips/blob/master/bip-0064.mediawiki

NODE_BLOOM:
https://github.com/bitcoin/bips/blob/master/bip-0111.mediawiki

The relevant code is here:
https://github.com/bitcoin/bitcoin/blob/master/src/protocol.h#L228

The NODE_GETUTXO bit was included even though it is not supported by core.
(It is one of XT's features).

I think you need to be able to reasonably claim that the bit is useful and
will have actual users, before you can claim a bit.

You can also claim one of the free for all bits 24 - 31, but that is
supposed to be only temporary.

Giving a link to "thin blocks" would help promote discussion about its
merits.

On Mon, Mar 7, 2016 at 8:06 PM, G. Andrew Stone via bitcoin-dev <
bitcoin-dev@lists.linuxfoundation.org> wrote:

> The Bitcoin Unlimited client needs a services bit to indicate that the
> node is capable of communicating thin blocks.  We propose to use bit 4 as
> AFAIK bit 3 is already earmarked for Segregated Witness.
>
> Andrew
>
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