adjusted build for packaging and added example spec for use with icinga

Hello,

I adjusted the build for packaging and added an example spec for use with icinga from packages.icinga.org and a custom build version of pnp4nagios not using nagios paths.
Build is tested successfully with Centos 6, Fedora and SLES 11 SP3 on i386 and x86_64, Centos 5 fails because of missing dependecies.
Installation is tested successfully on Centos 6 and SLES 11 SP3 x86_64.

Perhaps it helps someone to package and add it to the distributions with some adjustments.

Regards,
 Dirk