Check in the new memory allocator that allows the heap to span multiple blocks.

git-svn-id: http://svn.code.sf.net/p/freertos/code/trunk@2267 1d2547de-c912-0410-9cb9-b8ca96c0e9e2
Check in the portable.h version required to use heap_5.c.

git-svn-id: http://svn.code.sf.net/p/freertos/code/trunk@2268 1d2547de-c912-0410-9cb9-b8ca96c0e9e2