ada: Guard compile-time evaluator against rewritten if-expressions

ada: Guard compile-time evaluator against rewritten if-expressions

A hopefully temporary fix for if-expression that has been rewritten into an
if-statement, where a object reference has the if-statement as its parent,
but is not part of the condition, then statements or else statements.

gcc/ada/ChangeLog:

	* exp_util.adb (Get_Current_Value_Condition): Guard against orphaned
	references in rewritten if-expressions.