GNUmakefile: add Girocco/Config.pm dependency for apache.conf
While it is possible to specify an alternate Girocco::Config
file to be used by shlib.sh (and therefore also by the
make-apache-conf.sh script), the common case is to use the
default Girocco::Config which is found in Girocco/Config.pm.
Add a dependency to the build rule for apache.conf so that
any changes to the default Girocco::Config will also automatically
cause a rebuild of apache.conf.
Signed-off-by: Kyle J. McKay <mackyle@gmail.com>