Merge of r5138: use of NGX_FILE_ERROR. Use NGX_FILE_ERROR for handling file operations errors. On Win32 platforms 0 is used to indicate errors in file operations, so comparing against either -1 or NGX_OK is not portable. This was not much of an issue in patched code, since only ngx_fd_info() test is actually reachable on Win32 and in worst case it might result in bogus error log entry. Patch by Piotr Sikora.