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/mlist.h

@@ -0,0 +1,81 @@
+#pragma once
+#ifndef _MAXSCALE_MLIST_H
+#define _MAXSCALE_MLIST_H
+/*
+ * 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 <maxscale/cdefs.h>
+#include "skygw_utils.h"
+
+MXS_BEGIN_DECLS
+
+typedef struct mlist_node_st mlist_node_t;
+
+typedef struct mlist_st
+{
+    skygw_chk_t    mlist_chk_top;
+    char*          mlist_name;
+    void (*mlist_datadel)(void *);  /**< clean-up function for data */
+    simple_mutex_t mlist_mutex; /**< protect node updates and clean-up */
+    bool           mlist_uselock;
+    bool           mlist_islocked;
+    bool           mlist_deleted;
+    size_t         mlist_nodecount;
+    size_t         mlist_nodecount_max; /**< size limit. 0 == no limit */
+    size_t         mlist_versno;
+    bool           mlist_flat;
+    mlist_node_t*  mlist_first;
+    mlist_node_t*  mlist_last;
+    skygw_chk_t    mlist_chk_tail;
+} mlist_t;
+
+typedef struct mlist_cursor_st
+{
+    skygw_chk_t   mlcursor_chk_top;
+    mlist_t*      mlcursor_list;
+    mlist_node_t* mlcursor_pos;
+    pthread_t*    mlcursor_owner_thr;
+    skygw_chk_t   mlcursor_chk_tail;
+} mlist_cursor_t;
+
+struct mlist_node_st
+{
+    skygw_chk_t   mlnode_chk_top;
+    mlist_t*      mlnode_list;
+    mlist_node_t* mlnode_next;
+    void*         mlnode_data;
+    bool          mlnode_deleted;
+    skygw_chk_t   mlnode_chk_tail;
+};
+
+
+mlist_t*      mlist_init(mlist_t*         mlist,
+                         mlist_cursor_t** cursor,
+                         char*            name,
+                         void           (*datadel)(void*),
+                         int              maxnodes);
+void          mlist_done(mlist_t* list);
+bool          mlist_add_data_nomutex(mlist_t* list, void* data);
+bool          mlist_add_node_nomutex(mlist_t* list, mlist_node_t* newnode);
+mlist_node_t* mlist_detach_first(mlist_t* ml);
+mlist_node_t* mlist_detach_nodes(mlist_t* ml);
+void*         mlist_node_get_data(mlist_node_t* node);
+void          mlist_node_done(mlist_node_t* n);
+
+mlist_cursor_t* mlist_cursor_init(mlist_t* ml);
+void*           mlist_cursor_get_data_nomutex(mlist_cursor_t* c);
+bool            mlist_cursor_move_to_first(mlist_cursor_t* c);
+
+MXS_END_DECLS
+
+#endif