2008-08-05  Robert Dewar  <dewar@adacore.com>

	* opt.ads (Warn_On_Biased_Representation): New flag
	
	* sem_ch13.adb:
	(Analyze_Attribute_Definition_Clause): Issue warning when biased
	representation is required.
	(Minimum_Size): Don't allow biasing if enum rep clause case
	
	* sem_warn.adb:
	(Set_Dot_Warning_Switch): Add handling of -gnatw.b/B switches
	(Set_Warning_Switch): Include -gnatw.b in -gnatwa, -gnatw.B in gnatws
	
	* usage.adb: Add lines for -gnatw.b/B switches

From-SVN: r138704