Support for 64 bit systems

The rsp plugin was not usable under 64 bit systems since 4bee44e0d28cc32373155538ef880dbc00ae5f9f because the long datatype was used more and more in the code. This datatype has different sizes depending on which system (depending on the used ABI) it is used. A brief overview about type sizes can be found at https://wiki.debian.org/ArchitectureSpecificsMemo