Tar/untar now correctly supports symlinks.

Fixed the file overwrite problem on Windows.

Conflicts:
	changelog.html

Absolutizing on the server side is easier and more compact.

http://jenkins.local/job/JOBNAME/configure will become
10%-faster in Chrome 14 and 20%-faster in IE 9.

$(e).next() may return undefined.
If 2nd argument of insertBefore is undefined,
IE9 complains "SCRIPT87: Invalid argument".
To insert newChild at the end, 2nd argument should be null.
http://www.w3.org/TR/2000/REC-DOM-Level-2-Core-20001113/core.html#ID-952280727

See http://www.prototypejs.org/api/ajax/options
  This can be provided either as a URL-encoded string or as any
  Hash-compatible object (basically anything), with properties representing
  parameters.

Prototype 1.5.1.1 encodes parameters, but 1.7.0 does not.
If Jenkins uses 1.7.0, he warns us of container's encoding
regardless of container's configuration.