Merge of Liblinear with sample weights version

[seanv507]

Hi, I would like to work on merging the sample weights version. Can you provide some guidance in terms of your own requirements?
My final goal is having a sample weights version in R (based on https://cran.r-project.org/web/packages/LiblineaR/index.html)
I have done the majority of the work,
but there are a few sticking points:

a) adding sample weights 'breaks' the interface for eg matlab and python versions
b) should one change the code to always use sample weights, or is the added computational cost too great?
c) currently I have merged the c++ code using conditional compilation because of b), however, this does not work for python and R (no conditional compilation), so it raises the worry of python/R code calling the library with the wrong compilation options.

eg I could

[simsong]

This issue was moved to angleto#8