Add nested_array to array proposal.
Improve writing of designation proposal.

Move definitions of designators, designator-lists and target objects
from s8.5.1 to s8.5.  Remove references to designation labels, target
sub-objects, and overriding during rewrite.  Rewrite the new material
concerning default initializer clause order and evaluating
initializations.  Reinstate s8.5.1/9.  Many spelling and other tweaks.