[GSoC 2016] Support for variables in ruby_curry

Over the last few days I was working on implementing the equation constrained operator (=:<=). After working on the first version algorithm for it, we realised that support for variables was an important component specifically needed to test the operator.

We then worked on adding support for Variables both in compile time(object code generation) and runtime(execution). The concept implemented is also called Narrowing. This support was implemented by means of a generator table which maps a data constructor with token value 4 to an expression. Currently the expressions are bound during compile time, but it is preffered if the same happens freshly during runtime. This will be my next task of focus.

The support for variables can be found in this commit.