Rename ssl_locl.h to internal.h

Match the other internal headers.

Change-Id: Iff7e2dd06a1a7bf993053d0464cc15638ace3aaa
Reviewed-on: https://boringssl-review.googlesource.com/4280
Reviewed-by: Adam Langley <agl@google.com>
diff --git a/ssl/s3_enc.c b/ssl/s3_enc.c
index d6383d7..8db0bd9 100644
--- a/ssl/s3_enc.c
+++ b/ssl/s3_enc.c
@@ -142,7 +142,7 @@
 #include <openssl/md5.h>
 #include <openssl/obj.h>
 
-#include "ssl_locl.h"
+#include "internal.h"
 
 
 static const uint8_t ssl3_pad_1[48] = {