rename the defines to make it clear that these are interface subclasses

Change-Id: I0ad2168f89f8c4fbb2d2324f60de1276d023b41c
Reviewed-on: https://code.wireshark.org/review/3579
Reviewed-by: Martin Kaiser <wireshark@kaiser.cx>
Tested-by: Martin Kaiser <wireshark@kaiser.cx>