* exp_util.ads, exp_util.adb (Following_Address_Clause): Modify
Has_Following_Address_Clause so that it returns the address
clause if present, rather than a boolean value.
* sem_ch3.adb (Analyze_Object_Declaration): use
Following_Address_Clause.
* exp_ch3.adb (Expand_N_Object_Declaration): When a tagged object
is initialized, insert tag assignment after object is frozen,
which may be after an address clause that follows the declaration.