bindgen.adb (Gen_Elab_Calls): Skip reference to elab entity if none exists (Gen_Elab_Calls): Complain if...

2014-07-17  Robert Dewar  <dewar@adacore.com>

	* bindgen.adb (Gen_Elab_Calls): Skip reference to elab
	entity if none exists (Gen_Elab_Calls): Complain if clash with
	No_Multiple_Elaboration.
	* s-rident.ads, restrict.ads: Add restriction No_Multiple_Elaboration.
	* sem_util.adb (Build_Elaboration_Entity): Skip building entity
	if not needed.
	* gnat_rm.texi: Document restriction No_Multiple_Elaboration.
	* sem_ch4.adb: Minor comment updates.

From-SVN: r212735