einfo.ads (Overlays_Constant): Document usage for E_Constant.

einfo.ads (Overlays_Constant): Document usage for E_Constant.

2015-11-12  Eric Botcazou  <ebotcazou@adacore.com>

	* einfo.ads (Overlays_Constant): Document usage for E_Constant.
	* freeze.adb (Warn_Overlay): Small reformatting.
	(Check_Address_Clause): Deal specifically with deferred
	constants.  For a variable or a non-imported constant
	overlaying a constant object and with initialization value,
	either remove the initialization or issue a warning.  Fix a
	couple of typos.
	* sem_util.adb (Note_Possible_Modification): Overhaul the condition for
	the warning on modified constants and use Find_Overlaid_Entity instead
	of doing it manually.
	* sem_ch13.adb (Analyze_Attribute_Definition_Clause): Compute and
	set Overlays_Constant once on entry.  Do not treat the overlaid
	entity as volatile.  Do not issue the warning on modified
	constants here.
	* gcc-interface/decl.c (gnat_to_gnu_entity) <E_Constant>: Remove
	over-restrictive condition for the special treatment of deferred
	constants.
	<E_Variable>: Remove obsolete associated code.

From-SVN: r230229