[Ada] Do not generate encodings for fixed-point types by default

[Pierre-Marie de Rodat]

This flips the default for the generation of encodings for fixed-point
types in the debugging information generated by the compiler.

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

gcc/ada/

        * exp_dbug.adb (Get_Encoded_Name): Generate encodings for fixed
        point types only if -fgnat-encodings=all is specified.
diff --git a/gcc/ada/exp_dbug.adb b/gcc/ada/exp_dbug.adb
--- a/gcc/ada/exp_dbug.adb
+++ b/gcc/ada/exp_dbug.adb
@@ -648,7 +648,7 @@ package body Exp_Dbug is
       --  Fixed-point case: generate GNAT encodings when asked to
 
       if Is_Fixed_Point_Type (E)
-        and then GNAT_Encodings /= DWARF_GNAT_Encodings_Minimal
+        and then GNAT_Encodings = DWARF_GNAT_Encodings_All
       then
          Get_External_Name (E, True, "XF_");
          Add_Real_To_Buffer (Delta_Value (E));