rewrite of sap_rfc_modules

I have re-written the SAP RFC modules so that they work with Ruby 1.9. 

The modules will not be accepted into the Rapid7 repository because they rely on an SDK that cannot be freely distributed. Unfortunately the SDK is available only to those who have access to the SAP Service Marketplace (SMP) and it cannot be legally distributed. In order to get access to the SAP Marketplace you need an S-ID, password and customer number. Alternatively the required library files (such as libsapnwrfc) can be extracted from a SAP system (such as the freely available test drive systems). The modules also require the NW RFC SDK ruby wrapper (http://rubygems.org/gems/nwrfc) from Martin Ceronio. These third party requirements are one of the reasons that the submission to the Metasploit Framework proved problematic.

After obtaining the SDK and/or lib files and placing them in /usr/sap/nwrfcsdk/lib folder, execute the commands below:

$ export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/usr/sap/nwrfcsdk/lib
$ cd metasploit
$ echo -e "gem 'ffi'\ngem 'nwrfc'\n" >> Gemfile
$ sudo bundle install
$ msfconsole

You will now be able to load and use the modules.