log_t::rename_resized(): Replaces create_log_file_rename()

delete_log_files(): Moved to a separate function. Also invoked
on a normal startup when the log is not being resized, to
remove any garbage log files.

create_log_file(): Remove the std::string& parameter.

os_file_delete_if_exists_func() [_WIN32]: Do not retry DeleteFile()
on ERROR_ACCESS_DENIED.