This checkin is preliminary work for a new restriction No_Use_Of_Entity.
No test needed, since no external effect yet!

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

2015-01-06  Robert Dewar  <dewar@adacore.com>

	* namet.ads: Document use of Boolean2 for No_Use_Of_Entity.
	* restrict.ads (No_Use_Of_Entity): New table.
	* sem_prag.adb (Process_Restrictions_Or_Restriction_Warnings):
	Ignore No_Use_Of_Entity (will be processed in parser).
	* snames.ads-tmpl: Add entry for Name_No_Use_Of_Entity.