Store capabilities of monitored server

Checking the version number in various places in the code gets confusing.
It's better to check the version in one place and record the relevant data.

server/modules/monitor/mariadbmon/mariadbserver.hh

@@ -72,14 +72,10 @@ struct NodeData
 class MariaDBServer
 {
 public:
-    enum class version
+    enum class server_type
     {
         UNKNOWN,            /* Totally unknown. Server has not been connected to yet. */
-        OLD,                /* Anything older than 5.5. These are no longer supported by the monitor. */
-        MARIADB_MYSQL_55,   /* MariaDB 5.5 series or MySQL 5.5 and later. Does not have gtid (on MariaDB) so
-                             * all gtid-related features (failover etc.) are disabled. */
-        MARIADB_100,        /* MariaDB 10.0 and greater. In practice though, 10.0.2 or greater is assumed.
-                             * All monitor features are on. */
+        NORMAL,             /* A normal MariaDB/MySQL server, possibly supported. */
         BINLOG_ROUTER       /* MaxScale binlog server. Requires special handling. */
     };
 
@@ -89,6 +85,15 @@ public:
         BINLOG_OFF
     };
 
+    // Class which encapsulates server capabilities depending on its version.
+    class Capabilities
+    {
+    public:
+        bool basic_support = false;         // Is the server version supported by the monitor at all?
+        bool gtid = false;                  // Supports MariaDB gtid? Required for failover etc.
+        bool max_statement_time = false;    // Supports max_statement_time?
+    };
+
     // This class groups some miscellaneous replication related settings together.
     class ReplicationSettings
     {
@@ -104,7 +109,9 @@ public:
     /* What position this server has in the monitor config? Used for tiebreaking between servers. */
     int m_config_index = 0;
 
-    version m_version = version::UNKNOWN;           /* Server version/type. */
+    server_type  m_srv_type = server_type::UNKNOWN; /* Server type. */
+    Capabilities m_capabilities;                    /* Server capabilities */
+
     int64_t m_server_id = SERVER_ID_UNKNOWN;        /* Value of @@server_id. Valid values are
                                                      * 32bit unsigned. */
     int64_t m_gtid_domain_id = GTID_DOMAIN_UNKNOWN; /* The value of gtid_domain_id, the domain which is used