Some copy-editing

Signed-off-by: Nicolai Hähnle <haehnle@or.uni-bonn.de>
Signed decompositions and Brion's theorem

Signed-off-by: Nicolai Hähnle <haehnle@or.uni-bonn.de>
Evaluation of f(P;1) and some copy-editing

Signed-off-by: Nicolai Hähnle <haehnle@or.uni-bonn.de>