Pull Request:  Code can now handle both x86 and x64

Hello,
I really like this piece of software, and hope that you will let me contribute some of my work back to you.

I've taken the code and modularized it some while adding a Linux Makefile.
I then changed it so that you can use both compiled in IP:Port or command line options without needing to recompile.
I've also gone ahead and implemented an x64 meterpreter loader. (via copy paste)

In the future, I'd like to have the 32 bit process spawn an x64 process if it sees itself on that archetecture.  The idea of pulling the correct meterpreter for the machine just appeals to me.
I may also implement something like reverse http or https to break through (trivial) firewalls.

I'm still mostly a script kiddie, but I hope you find this acceptable.

Sincerely,
Arthur Moore