Added VarDumpOptimizer / VarExportOptimizer . [ci skip]

Added VarDumpOptimizer / VarExportOptimizer, Using PHP internal function, not userland function calls.

ex:

    var_export(a); // print outputs
    let buf = var_export(a); // return php variables as strings 


Signed-off-by: Rack Lin <racklin@gmail.com>