Provide APR based Apache Tomcat Native library

Binary package hint: tomcat6

Starting Tomcat 6 results in the following INFO message in the logs:
APR based Apache Tomcat Native library which allows optimal performance in production environments was not found...

According to http://tomcat.apache.org/tomcat-6.0-doc/apr.html :
Tomcat can use the Apache Portable Runtime to provide superior scalability, performance, and better integration with native server technologies. [...] When APR is enabled, the HTTP connector will use sendfile for hadling large static files (all such files will be sent ansychronously using high performance kernel level calls), and will use a socket poller for keepalive, increasing scalability of the server. [...] The HTTPS connector will use a socket poller for keepalive, increasing scalability of the server. It also uses OpenSSL, which may be more optimized than JSSE depending on the processor being used, and can be complemented with many commercial accelerator components. [...] The AJP connector will use a socket poller for keepalive, increasing scalability of the server. As AJP is designed around a pool of persistent (or almost persistent) connections, this will reduce significantly the amount of processing threads needed by Tomcat.

All that seems good to have.