internal/gocore: add test for 1.13 core files

Now that 1.13 is out, add a core file from 1.13 to the test suite.

Change-Id: Ief751a2c43e43e4ebf44d7ed0057864ccb61b603
Reviewed-on: https://go-review.googlesource.com/c/debug/+/193118
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>

internal/gocore/gocore_test.go

diff --git a/internal/gocore/gocore_test.go b/internal/gocore/gocore_test.go
index b1567a3..28d8891 100644
--- a/internal/gocore/gocore_test.go
+++ b/internal/gocore/gocore_test.go
@@ -258,4 +258,5 @@
 	loadExampleVersion(t, "1.10")
 	loadExampleVersion(t, "1.11")
 	loadExampleVersion(t, "1.12.zip")
+	loadExampleVersion(t, "1.13.zip")
 }

internal/gocore/testdata/1.13.zip

diff --git a/internal/gocore/testdata/1.13.zip b/internal/gocore/testdata/1.13.zip
new file mode 100644
index 0000000..332944d
--- /dev/null
+++ b/internal/gocore/testdata/1.13.zip
Binary files differ