Better compiler versioning

index/native/alire-index-gtkada.ads

@@ -10,8 +10,8 @@ package Alire.Index.GtkAda is
                  Native ((Debian | Ubuntu => Packaged_As ("libgtkada16.1.0-dev"),
                           others          => Unavailable)),
 
-                 Dependencies =>
-                   GNAT.Project >= GNAT.V_7
+                 Available_When =>
+                   Compiler_Is_Native
                 );
 
 end Alire.Index.GtkAda;

index/native/alire-index-ncursesada.ads

@@ -10,8 +10,8 @@ package Alire.Index.NcursesAda is
               Native ((Debian | Ubuntu => Packaged_As ("libncursesada5-dev"),
                        others          => Unavailable)),
 
-              Dependencies =>
-                GNAT.Project >= GNAT.V_7
+              Available_When =>
+                Compiler_Is_Native
              );
 
    V_3 : constant Release :=
@@ -20,8 +20,8 @@ package Alire.Index.NcursesAda is
               Native ((Debian | Ubuntu => Packaged_As ("libncursesada3-dev"),
                        others          => Unavailable)),
 
-              Dependencies =>
-                GNAT.Project >= GNAT.V_7
+              Available_When =>
+                Compiler_Is_Native
              );
 
 end Alire.Index.NcursesAda;

src/alire-platforms.ads

@@ -3,12 +3,15 @@ package Alire.Platforms with Preelaborate is
    --  Platform information necessary for some releases
 
    type Compilers is (GNAT_Unknown,
-                      GNAT_FSF_7_X, -- Future proofing for Compiler_Is_Native
-                      GNAT_FSF_7_2,
-                      GNAT_FSF_7_3,
-                      GNAT_FSF_8_Or_Newer,   -- More future proofing
-                      GNAT_GPL_Unknown,
-                      GNAT_GPL_2017,);
+
+                      GNAT_FSF_Old,
+                      GNAT_FSF_7_2, -- Has known bugs compared to 2017
+                      GNAT_FSF_7_3_Or_Newer,
+
+                      GNAT_GPL_Old,
+                      GNAT_GPL_2017_Or_Newer);
+   --  We do a minimum of future proofing. Unless newer version have known problems we don't need to
+   --    isolate their versions
 
    type Operating_Systems is (GNU_Linux,
                               Windows,

src/alire-properties-dependencies.ads

@@ -26,7 +26,7 @@ private
    end record;
 
    overriding function Image (This : Availability_Checker) return String is
-     ("Availability resolver");
+     ("Availability_Resolver");
 
    function New_Property (Checker : Checker_Function;
                           Props   : Alire.Properties.Vector) return Vector is

src/alire-requisites-platform.ads

@@ -27,7 +27,7 @@ package Alire.Requisites.Platform with Preelaborate is
    function Compiler is new Compilers.Factory;
 
    function Compiler_Is_Native return Tree is
-     (Compiler < GNAT_GPL_2017 and Compiler /= GNAT_Unknown);
+     (Compiler >= GNAT_FSF_Old and Compiler < GNAT_GPL_Old);
 
    package Distributions is new Comparables
      (Ps.Distributions, Ps."<", Ps.Distributions'Image,