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/d1_meth.c b/ssl/d1_meth.c
index e323fff..9e9c7df 100644
--- a/ssl/d1_meth.c
+++ b/ssl/d1_meth.c
@@ -55,7 +55,7 @@
  * (eay@cryptsoft.com).  This product includes software written by Tim
  * Hudson (tjh@cryptsoft.com). */
 
-#include "ssl_locl.h"
+#include "internal.h"
 
 
 static const SSL_PROTOCOL_METHOD DTLS_protocol_method = {