Use the internal buffer of a spread directly to avoid memory allocations

... on large object heap when dealing with high spread counts.

This basically solves issue described here: http://vvvv.org/forum/cyclic-framerate-drops
Note: This commit depends on https://github.com/mrvux/FeralTic/pull/10 - I don't know how to do a commit properly which affects a forked submodule.