For an object of a class-wide interface type, the object declaration is
rewritten as a renaming with a new entity, and debug info was not being
generated for the renaming, preventing printing of the object's value
in gdb. The entity of the renaming is now marked as needing debug info.

Tested on x86_64-pc-linux-gnu, committed on trunk

2012-03-19  Gary Dismukes  <dismukes@adacore.com>

	* exp_ch3.adb (Expand_N_Object_Declaration): In
	the case of an object of a class-wide interface type, where the
	declaration is rewritten as a renaming, call Set_Debug_Info_Needed
	on the renaming entity so that Materialize_Entity will be
	set. Also, change existing call (for other than interface cases)
	to call Set_Debug_Info_Needed rather than Set_Needs_Debug_Info
	(as specified for that flag).