Add a -renegotiate-freely flag to bssl client.

I needed to toy with a server that renegotiated recently and this was
useful.

Change-Id: Id4e2adaaa2ecfc1c434a3bae199efb2fdacc41bf
Reviewed-on: https://boringssl-review.googlesource.com/19344
Commit-Queue: Steven Valdez <svaldez@google.com>
Reviewed-by: Steven Valdez <svaldez@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>

tool/client.cc

diff --git a/tool/client.cc b/tool/client.cc
index d3a3115..70b6319 100644
--- a/tool/client.cc
+++ b/tool/client.cc
@@ -135,6 +135,10 @@
         "An HTTP proxy server to tunnel the TCP connection through",
     },
     {
+        "-renegotiate-freely", kBooleanArgument,
+        "Allow renegotiations from the peer.",
+    },
+    {
         "", kOptionalArgument, "",
     },
 };
@@ -262,6 +266,10 @@
     SSL_set_session(ssl.get(), session.get());
   }
 
+  if (args_map.count("-renegotiate-freely") != 0) {
+    SSL_set_renegotiate_mode(ssl.get(), ssl_renegotiate_freely);
+  }
+
   if (resume_session) {
     SSL_set_session(ssl.get(), resume_session.get());
   }