pginstaller - pginst: Add parameter FlattenDirectories to zip task.

Log Message:
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Add parameter FlattenDirectories to zip task. Use this to build the ZIP files that don't include subdirs. Removes hacky workaround of this feature.

Fix missed reference to PGDIR that shouldn't be used anymore.

Modified Files:
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pginst:
pginst.proj (r1.7 -> r1.8)
(http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/pginstaller/pginst/pginst.proj.diff?r1=1.7&r2=1.8)
pginst/util/tasks:
zip.cs (r1.2 -> r1.3)
(http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/pginstaller/pginst/util/tasks/zip.cs.diff?r1=1.2&r2=1.3)