Added ParallelCompression option to Zip task
Added ParallelCompression option to Zip task

Work around for a race condition bug in Ionic.Zip that causes it to hang
or produce corrupt output with some files.

smallkid/msbuildtasks,AArnott/msbuildtasks,arekbee/msbuildtasks,stimpy77/msbuildtasks,wrozmiarek/msbuildtasks,jricke/msbuildtasks,loresoft/msbuildtasks