bug#3410: tar mode fails to open many valid files

[Paul Pogonyshev]

When I open a 'tar.gz' file in Emacs, it quite often fails with a
message similar to:

    File mode specification error: (error
    "ntWorkbookBuilder.SheetRecordCollectingListener.html\"
    title=\"class in org.apache.poi.hssf.eventuserm has size
    -137265917 - corrupted")

E.g. file at

    
http://apache.promotionalpro.com/poi/dev/bin/poi-bin-3.5-beta5-20090219.tar.gz

exhibits this error.  It can be extracted without problems with 'tar
-xzf ...' at command line, so it must be a bug in Emacs' tar mode.
Maybe it is too strict or doesn't handle some extension properly.

Paul