Exclude Always from stderr

We are using Always not for errors, but for output we don't want the user to
be able to mute. So it makes some sense to still output it to stdout.

src/simple_logging.adb

@@ -36,7 +36,9 @@ package body Simple_Logging is
                           (Level,
                            Message));
          begin
-            if Level < Stdout_Level then
+            if Level < Stdout_Level and then
+              (Level /= Always or else Treat_Always_As_Error)
+            then
                GNAT.IO.Put_Line (GNAT.IO.Standard_Error, Line);
             else
                GNAT.IO.Put_Line (GNAT.IO.Standard_Output, Line);

src/simple_logging.ads

@@ -42,7 +42,11 @@ package Simple_Logging with Preelaborate is
    --  busy status spinner).
 
    Stdout_Level : Levels := Always;
-   --  Any level < Stdout_Level will be output to stderr
+   --  Any level < Stdout_Level will be output to stderr, except for Always
+   --  (see below).
+
+   Treat_Always_As_Error : Boolean := False;
+   --  When True, Stdout_Level also applies to the Always level
 
    procedure Log (Message  : String;
                   Level    : Levels := Info;