* stdio-common/tst-put-error.c: New file.
* libio/fileops.c (_IO_new_file_xsputn): If overflow fails and no more
data would have to be written signal error.
* libio/oldfileops.c (_IO_old_file_xsputn): Likewise.
* libio/fileops.c (_IO_new_file_overflow): Use NULL not 0.