add CMake build-system

These commits add support for generating makefiles and projectfiles via the CMake Makefile Generator.
It includes two scripts to bind OMNeT++ and its INET module to CMake, as well as CMake-files capable of building the DarknetSim-project.

I tested it with CMake 2.8, the GNU Make 3.82 and Ninja 1.2 build-systems, GCC 4.8 and Clang 3.2 compilers and OMNeT++ 4.2 and OMNeT++ 4.3 libraries, all in their default configuration, on Linux x86_64. INET was always at version 20111118.

It does not interfere with the existing OMNeT++ IDE projectfile.