absolute before parts read them. This fix was motivated by a test
provoked reading the options before they were absoluticated. 

Added a special check for trying to remove buildout.exe, which fails
on windows and is generally pointless. :)


git-svn-id: http://svn.zope.org/repos/main/zc.buildout/trunk@88545 62d5b8a3-27da-0310-9561-8e5933582275