Improve error message reporting when shared memory segment creation fails.
Improve error message reporting when shared memory segment creation fails.

crowell/modpagespeed_tmp,crowell/modpagespeed_tmp,crowell/modpagespeed_tmp,crowell/modpagespeed_tmp,crowell/modpagespeed_tmp,crowell/modpagespeed_tmp,crowell/modpagespeed_tmp