Change TLSEXT_IDX_* values into an enum

Perl changes reviewed by Richard Levitte. Non-perl changes reviewed by Rich
Salz

Reviewed-by: Rich Salz <rsalz@openssl.org>
Reviewed-by: Richard Levitte <levitte@openssl.org>
diff --git a/ssl/statem/extensions_srvr.c b/ssl/statem/extensions_srvr.c
index 9763c47..1eeae09 100644
--- a/ssl/statem/extensions_srvr.c
+++ b/ssl/statem/extensions_srvr.c
@@ -413,7 +413,7 @@
          * does nothing.
          */
         for (i = 0; i < srtp_pref; i++) {
-            const SRTP_PROTECTION_PROFILE *sprof =
+            SRTP_PROTECTION_PROFILE *sprof =
                 sk_SRTP_PROTECTION_PROFILE_value(srvr, i);
 
             if (sprof->id == id) {