[Ada] Remove degenerate Treat_Fixed_As_Integer mechanism

[Ada] Remove degenerate Treat_Fixed_As_Integer mechanism

2020-06-02  Eric Botcazou  <ebotcazou@adacore.com>

gcc/ada/

	* exp_ch4.adb (Expand_N_Op_Divide): Remove code dealing with
	the Treat_Fixed_As_Integer flag.
	(Expand_N_Op_Multiply): Likewise.
	* exp_fixd.adb (Build_Divide): Do the division in an integer
	type long enough to hold both operands and convert the result
	to the type of the LHS.  Do not set Treat_Fixed_As_Integer.
	(Build_Multiply): Do not set Treat_Fixed_As_Integer.
	(Build_Rem): Likewise.
	* sem_ch4.adb (Analyze_Arithmetic_Op): Remove code dealing with
	the Treat_Fixed_As_Integer flag.
	(Check_Arithmetic_Pair): Likewise.
	* sinfo.ads (Treat_Fixed_As_Integer): Delete.
	(N_Has_Treat_Fixed_As_Integer): Likewise.
	(Set_Treat_Fixed_As_Integer): Likewise.
	* sinfo.adb (Treat_Fixed_As_Integer): Likewise.
	(Set_Treat_Fixed_As_Integer): Likewise.
	* sprint.ads (Syntax Extensions): Remove '#' special character.
	* sprint.adb (Process_TFAI_RR_Flags): Delete.
	(Sprint_Node_Actual) <N_Op_Divide>: Print '@' manually.
	<N_Op_Multiply>: Likewise.
	<N_Op_Mod>: Do not print '#'.
	<N_Op_Rem>: Likewise.