[Ada] Cleanup routine for handling SPARK_Mode kinds

[Marc Poulhiès via Gcc-patches]

Code cleanup; semantics is unaffected.

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

gcc/ada/

        * sem_prag.adb (Get_SPARK_Mode_Type): Fix header box; replace
        chained IF with a CASE statement.
diff --git a/gcc/ada/sem_prag.adb b/gcc/ada/sem_prag.adb
--- a/gcc/ada/sem_prag.adb
+++ b/gcc/ada/sem_prag.adb
@@ -31172,25 +31172,26 @@ package body Sem_Prag is
       end if;
    end Get_Base_Subprogram;
 
-   -----------------------
+   -------------------------
    -- Get_SPARK_Mode_Type --
-   -----------------------
+   -------------------------
 
    function Get_SPARK_Mode_Type (N : Name_Id) return SPARK_Mode_Type is
    begin
-      if N = Name_Auto then
-         return None;
-      elsif N = Name_On then
-         return On;
-      elsif N = Name_Off then
-         return Off;
+      case N is
+         when Name_Auto =>
+            return None;
+         when Name_On =>
+            return On;
+         when Name_Off =>
+            return Off;
 
-      --  Any other argument is illegal. Assume that no SPARK mode applies to
-      --  avoid potential cascaded errors.
+         --  Any other argument is illegal. Assume that no SPARK mode applies
+         --  to avoid potential cascaded errors.
 
-      else
-         return None;
-      end if;
+         when others =>
+            return None;
+      end case;
    end Get_SPARK_Mode_Type;
 
    ------------------------------------