Need a better way to order Types in headers

[Jeff Johnson]

It would be nice to have something like ACorder for ArchType (ATorder?).
Some headers, particularly where we've globbed together a bunch of upstream
headers into one, and then uplifted which then adds grouping by LSB version,
have ordering issues in the Types.

i.e. Struct foo uses Type bar, but Type bar is 50 lines down the header *after*
Struct foo. This upsets devchk, and presumably may cause issues with an actual
app compiling too.

We have the HeaderGroup facility, which I've used, but that can get messy (and
maybe real messy for the next uplift), if you have to split the header up into
several groups to achieve the order needed if there is more than one of the
above instances.