Fix SSL_set_session documentation comment.

I put an extra space in there. Also document ownership and return value.

Change-Id: I0635423be7774a7db54dbf638cc548d291121529
Reviewed-on: https://boringssl-review.googlesource.com/6010
Reviewed-by: Adam Langley <agl@google.com>

include/openssl/ssl.h

diff --git a/include/openssl/ssl.h b/include/openssl/ssl.h
index 146a8a0..01bd7cc 100644
--- a/include/openssl/ssl.h
+++ b/include/openssl/ssl.h
@@ -1331,8 +1331,9 @@
  * |ctx| */
 OPENSSL_EXPORT int SSL_CTX_get_session_cache_mode(const SSL_CTX *ctx);
 
- /* SSL_set_session, for a client, configures |ssl| to offer to resume |session|
- * in the initial handshake. */
+/* SSL_set_session, for a client, configures |ssl| to offer to resume |session|
+ * in the initial handshake and returns one. The caller retains ownership of
+ * |session|. */
 OPENSSL_EXPORT int SSL_set_session(SSL *ssl, SSL_SESSION *session);
 
 /* SSL_get_session returns a non-owning pointer to |ssl|'s session. Prior to the