Skip ec_point_format if min_version >= TLS 1.3.

Trim a few more bytes from the future QUIC ClientHello.

Change-Id: If23c5cd078889a9a26cf2231b51b17c2615a38ea
Reviewed-on: https://boringssl-review.googlesource.com/12000
Reviewed-by: Steven Valdez <svaldez@google.com>
Reviewed-by: David Benjamin <davidben@google.com>
Commit-Queue: David Benjamin <davidben@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>

ssl/t1_lib.c

diff --git a/ssl/t1_lib.c b/ssl/t1_lib.c
index 83bae27..a265a2e 100644
--- a/ssl/t1_lib.c
+++ b/ssl/t1_lib.c
@@ -1853,6 +1853,16 @@
 }
 
 static int ext_ec_point_add_clienthello(SSL *ssl, CBB *out) {
+  uint16_t min_version, max_version;
+  if (!ssl_get_version_range(ssl, &min_version, &max_version)) {
+    return 0;
+  }
+
+  /* The point format extension is unneccessary in TLS 1.3. */
+  if (min_version >= TLS1_3_VERSION) {
+    return 1;
+  }
+
   return ext_ec_point_add_extension(ssl, out);
 }