Apache2 doesn't load mod_cluster modules - jboss

Question

I'm working on a debian jessie machine instantiated inside open nebula with kvm. I have to install jboss eap and mod_cluster, so I need to install the apache2 service.
I followed the mod_cluster quick start guide and set the /etc/apache2/apache2.conf file as follow:
LoadModule proxy_module modules/mod_proxy.so
LoadModule proxy_ajp_module modules/mod_proxy_ajp.so
LoadModule slotmem_module modules/mod_slotmem.so
LoadModule manager_module modules/mod_manager.so
LoadModule proxy_cluster_module modules/mod_proxy_cluster.so
LoadModule advertise_module modules/mod_advertise.so
ServerName master
Listen 10.0.0.6:6666
<VirtualHost 10.0.0.6:6666>
<Directory />
Order deny,allow
Deny from all
Allow from 10.0.0.
</Directory>
KeepAliveTimeout 60
MaxKeepAliveRequests 0
ManagerBalancerName nebula
AdvertiseFrequency 5
<Location /mod_cluster_manager>
Order deny,allow
Deny from all
Allow from 10.0.0.
</Location>
When I run the command /etc/init.d/apache2 start it return error, systemctl status apache2.service -l shows me:
apache2.service - LSB: Apache2 web server
Loaded: loaded (/etc/init.d/apache2)
Active: failed (Result: exit-code) since Wed 2015-12-16 15:17:45 CET; 10min ago
Process: 844 ExecStart=/etc/init.d/apache2 start (code=exited, status=1/FAILURE)
Dec 16 15:17:45 debian apache2[844]: Starting web server: apache2 failed!
Dec 16 15:17:45 debian apache2[844]: The apache2 configtest failed. ... (warning).
Dec 16 15:17:45 debian apache2[844]: Output of config test was:
Dec 16 15:17:45 debian apache2[844]: apache2: Syntax error on line 1 of /etc/apache2/apache2.conf: Cannot load modules/mod_proxy.so into server: /etc/apache2/modules/mod_proxy.so: undefined symbol: ap_escape_html
Dec 16 15:17:45 debian apache2[844]: Action 'configtest' failed.
Dec 16 15:17:45 debian apache2[844]: The Apache error log may have more information.
Dec 16 15:17:45 debian systemd[1]: apache2.service: control process exited, code=exited status=1
Dec 16 15:17:45 debian systemd[1]: Failed to start LSB: Apache2 web server.
Dec 16 15:17:45 debian systemd[1]: Unit apache2.service entered failed state.
I can't understand what "undefined symbol: ap_escape_html" means and how I could resolve it.
Thanks in advance for help.
UPDATE 1: I tried to build httpd from source. I installed the pcre libraries also from source, but when I run PREFIX/bin/apachectl -k start it returns the following error:
/etc/httpd/bin/httpd: error while loading shared libraries: libpcre.so.1: cannot open shared object file: No such file or directory

Answer 1

I solved libraries problems following this guide