Detect C++ preprocessor to make sure that gmpxx.h header
is detected properly both by preprocessor and compiler.
Detect apache group from /etc/group entries instead of default www-data.
Change configure option help strings to default toggle.
Use more standard 'geometry' package instead of 'a4wide'.
Package cgroup-bin is not necessary on Debian.
Add package install commands for RedHat-like distros.
Add git to list of required packages for development.
Update ChangeLog.