Name core tests consistently

Now, given a concept xyz,
* the main test file is called test_xyz.cc
* the executable is called test_xyz, and
* the ctest test is called text_xyz.

server/core/test/test_http.cc

@@ -0,0 +1,39 @@
+/*
+ * Copyright (c) 2016 MariaDB Corporation Ab
+ *
+ * Use of this software is governed by the Business Source License included
+ * in the LICENSE.TXT file and at www.mariadb.com/bsl11.
+ *
+ * Change Date: 2020-01-01
+ *
+ * On the date above, in accordance with the Business Source License, use
+ * of this software will be governed by version 2 or later of the General
+ * Public License.
+ */
+
+#include <iostream>
+
+#include <maxscale/debug.h>
+#include <maxscale/http.hh>
+
+using std::string;
+using std::cout;
+using std::endl;
+
+int main(int argc, char** argv)
+{
+    time_t now = time(NULL);
+    string date = http_to_date(now);
+    time_t converted_now = http_from_date(date);
+    string converted_date = http_to_date(converted_now);
+
+    cout << "Current linux time: " << now << endl;
+    cout << "HTTP-date from current time: " << date << endl;
+    cout << "Converted Linux time: " << converted_now << endl;
+    cout << "Converted HTTP-date: " << converted_date << endl;
+
+    ss_dassert(now == converted_now);
+    ss_dassert(date == converted_date);
+
+    return 0;
+}