[Ada] Implement Machine_Rounding attribute in line when possible

[Ada] Implement Machine_Rounding attribute in line when possible

GNAT implements Machine_Rounding as an alias for Rounding but, whereas
the implementation of the latter is in line when possible, that of the
former is always out of line, which is not aligned with the intent of
the Ada RM.

This changes the compiler to using for Machine_Rounding the same in line
implementation as Rounding when possible.

Running these commands:

  gcc -c f.adb -gnatD
  grep system f.adb.dg

On the following sources:

function F (Val : Float) return Integer is
begin
  return Integer (Float'Machine_Rounding (Val));
end;

Should execute silently.

2019-09-19  Eric Botcazou  <ebotcazou@adacore.com>

gcc/ada/

	* exp_attr.adb (Is_Inline_Floating_Point_Attribute): Treat
	Machine_Rounding as an alias for Rounding.
	* sem_res.adb (Simplify_Type_Conversion): Likewise.

From-SVN: r275943