Add brackets in lwIP assert statement to prevent compiler warnings.

git-svn-id: http://svn.code.sf.net/p/freertos/code/trunk@2243 1d2547de-c912-0410-9cb9-b8ca96c0e9e2
Add lwIP driver into Zynq demo - not yet fully functional.

git-svn-id: http://svn.code.sf.net/p/freertos/code/trunk@2244 1d2547de-c912-0410-9cb9-b8ca96c0e9e2