Have parse_elements() flag each item as "present (and not truncated)",

Have parse_elements() flag each item as "present (and not truncated)",
"present but truncated", and "not present", and don't have it return an
indication of whether we ran past the end of a packet - instead, have
the routines that handle particular management frame types use macros
that check what the status of a particular tagged parameter is and:

	print it if present and not truncated;

	skip it if not present;

	return a "packet truncated" indication if present but truncated.

This means we handle tagged parameters that aren't present, and print
parameters that are present and not truncated even if there's a
present-but-truncated field after them.

Add some additional bounds checks.

Make the table of rates bigger - there can be more than 8 rates in a
rates tagged parameter.