Add draft23 tests.

Change-Id: Ic77bc2f55e1e997ea20641cae66b0deddf1ef99c
Reviewed-on: https://boringssl-review.googlesource.com/25084
Commit-Queue: Steven Valdez <svaldez@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>
Reviewed-by: David Benjamin <davidben@google.com>

ssl/test/runner/runner.go

@@ -1367,6 +1367,13 @@ var tlsVersions = []tlsVersion{
 		versionWire:  tls13Draft22Version,
 		tls13Variant: TLS13Draft22,
 	},
+	{
+		name:         "TLS13Draft23",
+		version:      VersionTLS13,
+		excludeFlag:  "-no-tls13",
+		versionWire:  tls13Draft23Version,
+		tls13Variant: TLS13Draft23,
+	},
 	{
 		name:         "TLS13Experiment2",
 		version:      VersionTLS13,