Add tests for the point format extension.

Upstream accidentally started rejecting server-sent point formats in
https://github.com/openssl/openssl/issues/2133. Our own test coverage
here is also lacking, so flesh it out.

Change-Id: I99059558bd28d3a540c9687649d6db7e16579d29
Reviewed-on: https://boringssl-review.googlesource.com/12979
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>
diff --git a/ssl/test/runner/handshake_server.go b/ssl/test/runner/handshake_server.go
index 6499806..8f4e97b 100644
--- a/ssl/test/runner/handshake_server.go
+++ b/ssl/test/runner/handshake_server.go
@@ -1192,6 +1192,10 @@
 		serverExtensions.ticketSupported = true
 	}
 
+	if c.config.Bugs.SendSupportedPointFormats != nil {
+		serverExtensions.supportedPoints = c.config.Bugs.SendSupportedPointFormats
+	}
+
 	if !hs.clientHello.hasGREASEExtension && config.Bugs.ExpectGREASE {
 		return errors.New("tls: no GREASE extension found")
 	}