IE elements in various management frames are ordered. This ordering is
outlined in 802.11, Section 9.3.3. The ordering is actually different
depending on the frame type. Instead of trying to implement the order
manually, add a utility function that will sort the IEs in the order
expected by the particular management frame type.
Since we already have IE ordering look up tables in the various
management frame type validation functions, move them to global level
and re-use these lookup tables for the sorting utility.
Validate the IE order for some of the cases. For other cases, as with
the Disassociation, Deauthentication and Action frame types in section
9.3 it's not even clear from the spec the fields are expected to be IEs
(in fact for Action frame we know they aren't). For the Shared Key
authentication type drop the union with the contents as they can be
easier parsed as an IE sequence. For SAE we are not expecting an IE
sequence apparently so this is where the union could come useful but
let's leave that until we want to support SAE.
Declare the two missing frame subtype enum values for Action frames,
assume Action frames are valid. Once we have specific validation code
for any Action frames elsewhere, we can move it to mpdu_validate, but
right don't try to validate the frame body as there are many subtypes
and we don't use any of them except Neighbor Reports which are actually
really simple.
Refactor management frame structures to take into account optional
presence of some parts of the header:
* drop the single structure for management header and body since
the body offset is variable.
* add mmpdu_get_body to locate the start of frame body.
* drop the union of different management frame type bodies.
* prefix names specific to management frames with "mmpdu" instead
of "mpdu" including any enums based on 802.11-2012 section 8.4.
* move the FC field to the mmpdu_header structure.
What comes in is a frame, and let's set it to uint8_t pointer, which is
semantically better than unsigned char.
Also, returning the cast pointer instead of a boolean is easier to
use as there won't be any need to perform the cast ourselves afterward
