Move the SSL3_CK_CIPHERSUITE_FLAG out of public header

The newly added SSL3_CK_CIPHERSUITE_FLAG shouldn't be in a public header
file

Reviewed-by: Rich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/2259)
diff --git a/ssl/s3_lib.c b/ssl/s3_lib.c
index bdb4cb4..c4d4352 100644
--- a/ssl/s3_lib.c
+++ b/ssl/s3_lib.c
@@ -3566,7 +3566,7 @@
 
 int ssl3_put_cipher_by_char(const SSL_CIPHER *c, WPACKET *pkt, size_t *len)
 {
-    if ((c->id & 0xff000000) != 0x03000000) {
+    if ((c->id & 0xff000000) != SSL3_CK_CIPHERSUITE_FLAG) {
         *len = 0;
         return 1;
     }