Move headers from server/include to include/maxscale

- Headers now to be included as <maxscale/xyz.h>
- First step, no cleanup of headers has been made. Only moving
  from one place to another + necessary modifications.

include/maxscale/statistics.h

@@ -0,0 +1,71 @@
+#ifndef _STATISTICS_HG
+#define _STATISTICS_HG
+/*
+ * 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/bsl.
+ *
+ * Change Date: 2019-07-01
+ *
+ * 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 statistics.h  - Lock-free statistics gathering
+ *
+ * @verbatim
+ * Revision History
+ *
+ * Date         Who                 Description
+ * 21/01/16     Markus Makela       Initial implementation
+ * 15/06/16     Martin Brampton     Frequently used functions inlined
+ * @endverbatim
+ */
+
+#include <stdint.h>
+
+typedef void* ts_stats_t;
+
+/** stats_init should be called only once */
+void ts_stats_init();
+
+/** No-op for now */
+void ts_stats_end();
+
+ts_stats_t ts_stats_alloc();
+void ts_stats_free(ts_stats_t stats);
+int64_t ts_stats_sum(ts_stats_t stats);
+
+/**
+ * @brief Increment thread statistics by one
+ *
+ * @param stats     Statistics to add to
+ * @param thread_id ID of thread
+ */
+static void inline
+ts_stats_increment(ts_stats_t stats, int thread_id)
+{
+    ((int64_t*)stats)[thread_id]++;
+}
+
+/**
+ * @brief Assign a value to a statistics element
+ *
+ * This sets the value for the specified thread.
+ *
+ * @param stats     Statistics to set
+ * @param value     Value to set to
+ * @param thread_id ID of thread
+ *
+ * @note Appears to be unused
+ */
+static void inline
+ts_stats_set(ts_stats_t stats, int value, int thread_id)
+{
+    ((int64_t*)stats)[thread_id] = value;
+}
+
+#endif