Well I finally managed to get the 2.20 CVS version to compile. But it wasn't easy.
I took the makefile for amule 2.1.3 as a template.
Next i deleted some of the patches, and modified some others.
On my build environment zlib-detection during ./configure somehow fails, i solved it by patching configure.in and acinclude.m4 to use zlib-detection from 2.1.3
Finally building fails on a line in Scanner.l, i solved that by a patch that removes that line.
There might be one or two other things i did manually, I'll see if i can remember them, and post them here aswell