Let ssl_get_cipher_by_char yield not-valid ciphers

Now that we have made SCSVs into more of a first-class object, provide
a way for the bytes-to-SSL_CIPHER conversion to actually return them.
Add a flag 'all' to ssl_get_cipher_by_char to indicate that we want
all the known ciphers, not just the ones valid for encryption.  This will,
in practice, let the caller retrieve the SCSVs.

Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Richard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/2279)
diff --git a/ssl/statem/statem_clnt.c b/ssl/statem/statem_clnt.c
index 614da1b..bc35a3e 100644
--- a/ssl/statem/statem_clnt.c
+++ b/ssl/statem/statem_clnt.c
@@ -1294,7 +1294,7 @@
                      && master_key_length > 0) {
                 s->session->master_key_length = master_key_length;
                 s->session->cipher = pref_cipher ?
-                    pref_cipher : ssl_get_cipher_by_char(s, cipherchars);
+                    pref_cipher : ssl_get_cipher_by_char(s, cipherchars, 0);
             } else {
                 SSLerr(SSL_F_TLS_PROCESS_SERVER_HELLO, ERR_R_INTERNAL_ERROR);
                 al = SSL_AD_INTERNAL_ERROR;
@@ -1353,7 +1353,7 @@
         goto f_err;
     }
 
-    c = ssl_get_cipher_by_char(s, cipherchars);
+    c = ssl_get_cipher_by_char(s, cipherchars, 0);
     if (c == NULL) {
         /* unknown cipher */
         al = SSL_AD_ILLEGAL_PARAMETER;