Fix deprecation macros for old Sun C. [skip ci]

As Francois-Xavier points it out, my recent commit 5265743 in certain
contexts adds rather than removes compiler warnings:

cc: Sun C 5.12 SunOS_i386 Patch 148918-11 2017/12/13
"tcpdump.c", line 3267: warning: bad message tag: E_DEPRECATED_ATT
"tcpdump.c", line 3307: warning: bad message tag: E_DEPRECATED_ATT

Get Sun C versions right to fix that.

Author: infrastation

diag-control.h

@@ -178,12 +178,17 @@
    */
 #elif ND_IS_AT_LEAST_SUNC_VERSION(5,5)
   /*
-   * Suppress deprecation warnings.
+   * error_messages() is a valid pragma.
    */
-  #define DIAG_OFF_DEPRECATION \
-    DIAG_DO_PRAGMA(error_messages(off,E_DEPRECATED_ATT))
-  #define DIAG_ON_DEPRECATION \
-    DIAG_DO_PRAGMA(error_messages(default,E_DEPRECATED_ATT))
+  #if ND_IS_AT_LEAST_SUNC_VERSION(5,13)
+    /*
+     * E_DEPRECATED_ATT is a valid warning tag.
+     */
+    #define DIAG_OFF_DEPRECATION \
+      DIAG_DO_PRAGMA(error_messages(off,E_DEPRECATED_ATT))
+    #define DIAG_ON_DEPRECATION \
+      DIAG_DO_PRAGMA(error_messages(default,E_DEPRECATED_ATT))
+  #endif
 #endif
 
 /*