MXS-2008 Provide single entrypoint for initializing maxbase

Everything of maxbase can now be initialized by a call to

    maxbase_init();

(from a C-program) or

    maxbase::init();

from a C++-program and finalized with calls to either
maxbase_finish() or maxbase::finish(). Creating an instance
maxbase::MaxBase will take care of both operations.

maxutils/maxbase/include/maxbase/maxbase.hh

@@ -0,0 +1,109 @@
+#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: 2022-01-01
+ *
+ * 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 <maxbase/ccdefs.hh>
+#include <stdexcept>
+#include <maxbase/log.h>
+#include <maxbase/maxbase.h>
+
+namespace maxbase
+{
+
+/**
+ * @brief Initializes the maxbase library
+ *
+ * This function should be called before any other functionality of
+ * maxbase is used. A notable exception is the maxbase log that can
+ * be initialized and used independently.
+ *
+ * Note that if an instance of @c MaxBase is created, it will call
+ * both @init and @finish.
+ *
+ * @return True, if maxbase could be initialized, false otherwise.
+ */
+bool init();
+
+/**
+ * @brief Finalizes the maxbase library
+ *
+ * This function should be called before program exit, if @c init()
+ * returned true.
+ */
+void finish();
+
+
+/**
+ * @class MaxBase
+ *
+ * A simple utility RAII class where the constructor initializes maxbase
+ * (and optionally the log) and the destructor finalizes it.
+ */
+class MaxBase
+{
+    MaxBase(const MaxBase&) = delete;
+    MaxBase& operator=(const MaxBase&) = delete;
+
+public:
+    /**
+     * @brief Initializes MaxBase but not the MaxBase log.
+     */
+    MaxBase()
+        : m_log_inited(false)
+    {
+        if (!maxbase_init())
+        {
+            throw std::runtime_error("Initialization of maxbase failed.");
+        }
+    }
+
+    /**
+     * @brief Initializes MaxBase and the MaxBase log.
+     *
+     * @see mxb_log_init
+     *
+     * @throws std::runtime_error if the initialization failed.
+     */
+    MaxBase(const char* zIdent,
+            const char* zLogdir,
+            const char* zFilename,
+            mxb_log_target_t target,
+            mxb_log_context_provider_t context_provider);
+
+    /**
+     * @brief Initializes MaxBase and the MaxBase log.
+     *
+     * @see mxb_log_init
+     *
+     * @throws std::runtime_error if the initialization failed.
+     */
+    MaxBase(mxb_log_target_t target)
+        : MaxBase(nullptr, ".", nullptr, target, nullptr)
+    {
+    }
+
+    ~MaxBase()
+    {
+        if (m_log_inited)
+        {
+            mxb_log_finish();
+        }
+
+        maxbase::finish();
+    }
+
+private:
+    bool m_log_inited;
+};
+
+}