const-ify some input SSL * arguments

These tiny functions only read from the input SSL, and we are
about to use them from functions that only have a const SSL* available,
so propagate const a bit further.
Reviewed-by: NMatt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/6378)

doc/man3/SSL_in_init.pod

@@ -14,9 +14,9 @@ SSL_get_state
 
  #include <openssl/ssl.h>
 
- int SSL_in_init(SSL *s);
- int SSL_in_before(SSL *s);
- int SSL_is_init_finished(SSL *s);
+ int SSL_in_init(const SSL *s);
+ int SSL_in_before(const SSL *s);
+ int SSL_is_init_finished(const SSL *s);
 
  int SSL_in_connect_init(SSL *s);
  int SSL_in_accept_init(SSL *s);

include/openssl/ssl.h

@@ -1058,9 +1058,9 @@ typedef enum {
 /* Is the SSL_connection established? */
 # define SSL_in_connect_init(a)          (SSL_in_init(a) && !SSL_is_server(a))
 # define SSL_in_accept_init(a)           (SSL_in_init(a) && SSL_is_server(a))
-int SSL_in_init(SSL *s);
-int SSL_in_before(SSL *s);
-int SSL_is_init_finished(SSL *s);
+int SSL_in_init(const SSL *s);
+int SSL_in_before(const SSL *s);
+int SSL_is_init_finished(const SSL *s);
 
 /*
  * The following 3 states are kept in ssl->rlayer.rstate when reads fail, you

ssl/statem/statem.c

@@ -68,17 +68,17 @@ OSSL_HANDSHAKE_STATE SSL_get_state(const SSL *ssl)
     return ssl->statem.hand_state;
 }
 
-int SSL_in_init(SSL *s)
+int SSL_in_init(const SSL *s)
 {
     return s->statem.in_init;
 }
 
-int SSL_is_init_finished(SSL *s)
+int SSL_is_init_finished(const SSL *s)
 {
     return !(s->statem.in_init) && (s->statem.hand_state == TLS_ST_OK);
 }
 
-int SSL_in_before(SSL *s)
+int SSL_in_before(const SSL *s)
 {
     /*
      * Historically being "in before" meant before anything had happened. In the