Get data directory for server commands if needed

Also add configuration file option "pgdata" for hard-coding the
node's data directory - if the "repmgr" DB user isn't a superuser
or doesn't have permission to extract the data directory, we'll
need another way of finding out.

repmgr-client-global.h

@@ -169,6 +169,6 @@ extern bool remote_command(const char *host, const char *user, const char *comma
 
 /* server control functions */
 extern void get_server_action(t_server_action action, char *script, char *data_dir);
-
-
+extern bool data_dir_required_for_action(t_server_action action);
+extern void get_node_data_directory(char *data_dir_buf);
 #endif