Fix in-source builds

The internal header directory conflicted with in-source builds causing a
build failure. This is fixed by renaming the internal header directory to
something other than maxscale.

The renaming pointed out a few problems in a couple of source files that
appeared to include internal headers when the headers were in fact public
headers.

Fixed maxctrl in-source builds by making the copying of the sources
optional.

server/core/internal/resource.hh

@@ -0,0 +1,98 @@
+#pragma once
+/*
+ * 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.
+ */
+
+/** @file REST API resources */
+
+#include <maxscale/cppdefs.hh>
+
+#include <string>
+#include <deque>
+
+#include <maxscale/server.h>
+#include <maxscale/http.hh>
+
+#include "httprequest.hh"
+#include "httpresponse.hh"
+#include "monitor.h"
+#include "service.h"
+#include "filter.h"
+#include "session.h"
+
+typedef HttpResponse (*ResourceCallback)(const HttpRequest& request);
+
+class Resource
+{
+    Resource(const Resource&);
+    Resource& operator = (const Resource&);
+public:
+
+    enum resource_constraint
+    {
+        NONE         = 0,
+        REQUIRE_BODY = (1 << 0)
+    };
+
+    Resource(ResourceCallback cb, int components, ...);
+    ~Resource();
+
+    /**
+     * @brief Check if a request matches this resource
+     *
+     * @param request Request to match
+     *
+     * @return True if this request matches this resource
+     */
+    bool match(const HttpRequest& request) const;
+
+    /**
+     * @brief Handle a HTTP request
+     *
+     * @param request Request to handle
+     *
+     * @return Response to the request
+     */
+    HttpResponse call(const HttpRequest& request) const;
+
+    /**
+     * Add a resource constraint
+     *
+     * @param type Constraint to add
+     */
+    void add_constraint(resource_constraint type);
+
+    /**
+     * Whether resource requires a request body
+     *
+     * @return True if resource requires a request body
+     */
+    bool requires_body() const;
+
+private:
+
+    bool matching_variable_path(const std::string& path, const std::string& target) const;
+
+    ResourceCallback        m_cb;          /**< Resource handler callback */
+    std::deque<std::string> m_path;        /**< Path components */
+    bool                    m_is_glob;     /**< Does this path glob? */
+    uint32_t                m_constraints; /**< Resource constraints */
+};
+
+/**
+ * @brief Handle a HTTP request
+ *
+ * @param request Request to handle
+ *
+ * @return Response to request
+ */
+HttpResponse resource_handle_request(const HttpRequest& request);