* plugin.cpp (includes): Remove GCC 5.0 unincludable files.
(global declaration): Add print decls.
(mypass): Remove use fields.
(build_type): Use print_node instead.
(build_function_decl): Use print_node instead; Make the return decl addressable.
(execute_trace): Make var decl addressable and its context binds to current_function_decl.
(class trace_pass): GCC 5.0 compatible.