[Ada] Error on T'Reduce of when T is not a container

[Pierre-Marie de Rodat]

This patch fixes a bug that caused the compiler to crash on T'Reduce, if
T is something like Integer.

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

gcc/ada/

        * sem_attr.adb (Analyze_Attribute): Change "$" to "&".
        Otherwise, Errout will trip over an uninitialized (invalid)
        variable (Error_Msg_Unit_1).
diff --git a/gcc/ada/sem_attr.adb b/gcc/ada/sem_attr.adb
--- a/gcc/ada/sem_attr.adb
+++ b/gcc/ada/sem_attr.adb
@@ -5682,7 +5682,7 @@ package body Sem_Attr is
                   null;
                else
                   Error_Msg_NE
-                    ("cannot apply Reduce to object of type$", N, Typ);
+                    ("cannot apply Reduce to object of type&", N, Typ);
                end if;
 
             elsif Present (Expressions (Stream))