[Ada] Send gnatls/gnatcmd verbose diagnostics to stderr

[Arnaud Charlet]

This change ensures that verbose debugging/diagnostics messages emitted
by gnatls/gnat list are sent to stderr instead of being interspersed with
the normal stdout output.

Tested on x86_64-pc-linux-gnu, committed on trunk

2011-12-21  Thomas Quinot  <qui...@adacore.com>

        * gnatls.adb (Gnatls): Call Set_Standard_Error at startup, and then
        Set_Standard_Output just before producing normal (non-diagnostic)
        output.
        * gnatcmd.adb (Gnatcmd): Call Set_Standard_Error at initialization
        (and again after parsing project files).


Index: gnatcmd.adb
===================================================================
--- gnatcmd.adb (revision 182572)
+++ gnatcmd.adb (working copy)
@@ -34,7 +34,7 @@
 with Namet;    use Namet;
 with Opt;      use Opt;
 with Osint;    use Osint;
-with Output;
+with Output;   use Output;
 with Prj;      use Prj;
 with Prj.Env;
 with Prj.Ext;  use Prj.Ext;
@@ -1375,6 +1375,10 @@
 --  Start of processing for GNATCmd
 
 begin
+   --  All output from GNATCmd is debugging or error output: send to stderr
+
+   Set_Standard_Error;
+
    --  Initializations
 
    Csets.Initialize;
@@ -1901,6 +1905,10 @@
             Env               => Root_Environment,
             Packages_To_Check => Packages_To_Check);
 
+         --  Prj.Pars.Parse calls Set_Standard_Output, reset to stderr
+
+         Set_Standard_Error;
+
          if Project = Prj.No_Project then
             Fail ("""" & Project_File.all & """ processing failed");
          end if;
Index: gnatls.adb
===================================================================
--- gnatls.adb  (revision 182572)
+++ gnatls.adb  (working copy)
@@ -1553,6 +1553,7 @@
    --  If -l (output license information) is given, it must be the only switch
 
    if License and then Arg_Count /= 2 then
+      Set_Standard_Error;
       Write_Str ("Can't use -l with another switch");
       Write_Eol;
       Usage;
@@ -1713,6 +1714,7 @@
             GNATDIST.Output_No_ALI (Lib_File_Name (Main_File));
 
          else
+            Set_Standard_Error;
             Write_Str ("Can't find library info for ");
             Get_Name_String (Main_File);
             Write_Char ('"'); -- "
@@ -1745,6 +1747,10 @@
       end if;
    end loop;
 
+   --  Reset default output file descriptor, if needed
+
+   Set_Standard_Output;
+
    if Very_Verbose_Mode then
       for A in ALIs.First .. ALIs.Last loop
          GNATDIST.Output_ALI (A);