[Ada] Remove non-ASCII character

[Pierre-Marie de Rodat]

This is the first step in supporting [...] notation for aggregates in
-gnatX mode.

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

gcc/ada/

        * libgnat/a-numeri.ads: Remove the greek letter.
diff --git a/gcc/ada/libgnat/a-numeri.ads b/gcc/ada/libgnat/a-numeri.ads
--- a/gcc/ada/libgnat/a-numeri.ads
+++ b/gcc/ada/libgnat/a-numeri.ads
@@ -21,10 +21,13 @@ package Ada.Numerics is
    Pi : constant :=
           3.14159_26535_89793_23846_26433_83279_50288_41971_69399_37511;
 
-   ["03C0"] : constant := Pi;
+   --  ["03C0"] : constant := Pi;
    --  This is the Greek letter Pi (for Ada 2005 AI-388). Note that it is
    --  conforming to have this constant present even in Ada 95 mode, as there
    --  is no way for a normal mode Ada 95 program to reference this identifier.
+   --  ???This is removed for now, because nobody uses it, and it causes
+   --  trouble for tools other than the compiler. If people want to use the
+   --  Greek letter in their programs, they can easily define it themselves.
 
    e : constant :=
          2.71828_18284_59045_23536_02874_71352_66249_77572_47093_69996;