Move the Zynq's lwIP example from the Full demo into its own configuration as having...

Move the Zynq's lwIP example from the Full demo into its own configuration as having the lwIP tasks at a high priority made the self checking test tasks report failures, while having the lwIP tasks at a low priority slugged the throughput.

git-svn-id: https://svn.code.sf.net/p/freertos/code/trunk@2253 1d2547de-c912-0410-9cb9-b8ca96c0e9e2