New setup.exe release candidate - please test

[Max Bowsher]

Version 2.459

 - Repair the broken detection of wrongly-sized package files.

 - Fix setup keeping open handles to every tarball it installs during a run.

 - Fix a miscellany of error-reporting deficiencies.

 - Close stdin, to protect against rogue postinstall scripts attempting to
   wait for user input.

http://www.cygwin.com/setup-snapshots/setup-2.459.exe

Also, this release appears in my testing to fix the hang when a new 
install-everything setup is attempted, as side-effect of other bugfixes.

Please test - if no regressions are discovered in the next few days, it will 
be promoted to the release version, accessible from the cygwin.com main 
page.

Max.