Ticket: 6724
Allows sugar syntax for bitflags keywords.
While the expressivity does not increase, because we could already
use numerial values with all generic integer modes, this modifier
prefix is used with the strings, and follows the syntax
that is already used for fragbits and tcp.flags keyword.
Ticket: 4863
On the way, convert some keywords to use the first-class integer
support.
And helpers for pure rust the support for multi-buffer.
Move the C unit tests about keyword mqtt.protocol_version
to unit tests for generic integer parsing, and test version 5
instead of testing twice version 3.
Also iterate all tx's messages for reason code as is done for other
keywords.
And allow detection on empty topics.