Remove NG from the names - it adds nothing.
Don't use the abbreviations for pcapng block names, spell out what the
block does (e.g. "WTAP_BLOCK_DECRYPTION_SECRETS" rather than
"WTAP_BLOCK_DSB"), to make it more obvious what the block does.
Spell out some other abbreviations.
Add WTAP_BLOCK_PACKET for future use for packet blocks; there's no need
to distinguish between the Enhanced Packet Block, the Simple Packet
Block, and the deprecated Packet Block here.
09684644ee