Rename ssl_sess.c to ssl_session.c.

Change-Id: Ib730ffe49b30c79b3f30acae4070f6055081a0a3
Reviewed-on: https://boringssl-review.googlesource.com/5878
Reviewed-by: Adam Langley <agl@google.com>
diff --git a/ssl/CMakeLists.txt b/ssl/CMakeLists.txt
index 5ba9c63..2785dcf 100644
--- a/ssl/CMakeLists.txt
+++ b/ssl/CMakeLists.txt
@@ -29,7 +29,7 @@
   ssl_file.c
   ssl_lib.c
   ssl_rsa.c
-  ssl_sess.c
+  ssl_session.c
   ssl_stat.c
   ssl_txt.c
   t1_enc.c