Cannot handle junk defined names

Created originally on Bitbucket by CharlieC

Some files have entries like

#!xml

<definedName name="_xlnm.Print_Titles">"Formula removed, name  can be deleted."</definedName>

Because the specification is so lax this is valid XML but still junk. openpyxl always expects print titles and print areas to be bound to specific worksheets. Only Excel would make these global constants and not attributes of specific worksheets.

Could skip over these but better to remove them.