Move various embedded target structs to the beginnings of
their containers ... pretty much the way C++ or Obj-C
would for single inheritance.

This shrinks code that accesses those embedded structs by
letting common offsets use smaller instructions.  Sample
before/after sizes (on amd64):

  17181	    312	      0	  17493	   4455	arm920t.o
  16810	    312	      0	  17122	   42e2	arm920t.o

Where the "after" is the smaller number, with this patch
over the ones leveraging that embedding knowledge.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>