[Ada] Remove unnecessary dead code after calls to nonreturning procedures

A new warning about unreachable code that follows calls to procedures
with No_Return would flag some dead defensive code. Comments next to
this code suggest that it was added to please some ancient version of
the compiler, but recent releases of GNAT do not require such a code.

gcc/ada/

	* gnatls.adb (Corresponding_Sdep_Entry): Remove dead return
	statement in defensive path; there is another return statement
	for a normal execution of this routine, so rule Ada RM 6.5(5),
	which requires function to have at least one return statement is
	still satisfied.
	(Gnatls): Remove dead, call to nonreturning Exit_Program after
	Output_License_Information which itself does not return.
	* libgnat/a-exstat.adb (Bad_EO): Remove raise statement that was
	meant to please some ancient version of GNAT.
	* libgnat/g-awk.adb (Raise_With_Info): Likewise.
	* sem_attr.adb (Check_Reference): Remove dead return statement;
	rule Ada RM 6.5(5), which requires function to have at least one
	return statement is still satisfied.
	(Analyze_Attribute): Remove dead exit statement.
	(Check_Reference): Same as above.
	* sem_ch12.adb (Instantiate_Formal_Package): Remove dead raise
	statement; it was inconsistent with other calls to
	Abandon_Instantiation, which are not followed by a raise
	statement.
	* sem_prag.adb (Process_Convention): Remove dead defensive
	assignment.
	(Interrupt_State): Remove dead defensive exit statement.
	(Do_SPARK_Mode): Likewise.
	* sfn_scan.adb (Scan_String): Remove dead defensive assignment.
7 files changed