Add test for issue #1452.

TCP connection should not crash the program if they are closed from within a finalizer. Instead, give a warning if such a class has leaked.

(cherry picked from commit 2c0adbc56170571991781cebf1e3aac1549828ad)

tests/vibe.core.net.1452/dub.sdl

@@ -0,0 +1,3 @@
+name "tests"
+description "Invalid memory operation on TCP connection leakage at shutdown"
+dependency "vibe-d:core" path="../../"

tests/vibe.core.net.1452/source/app.d

@@ -0,0 +1,23 @@
+import vibe.core.core;
+import vibe.core.net;
+import core.time : msecs;
+
+class C {
+	TCPConnection m_conn;
+
+	this()
+	{
+		m_conn = connectTCP("google.com", 443);
+	}
+
+	~this()
+	{
+		m_conn.close();
+	}
+}
+
+void main()
+{
+	auto c = new C;
+	// let druntime collect c during shutdown
+}