well I understood it like this (I hope I got it right:-)
downlaod source of apache2 => /usr/local/src
h898552:/usr/local/src/httpd-2.2.3# ./configure --prefix=/usr/local/apache2 --enable-proxy --enable-proxy-http --enable-cache --enable-mem_cache
these are the modules
still working on it... I thought I might need, then make, folowed by make install
=> I can start it from /usr/local/apache2/bin/apache2ctl start after modifying the "Listen localhost:88" so now it runs on port 88 and the original can continue running on port 80.
next step would be to copy /etc/apache2/apache2.conf to /usr/local/apache2/http.conf and change all relevant paths and ports that might disturb...