Phydef

[stevenrbrandt]

Add PhyDef:
PhyDef makes it possible to define two versions of the same function,
one that can be called from Phylanx and the other that can be called
from Python.

Example:

from phylanx import PhyDef
from numpy import zeros

with PhyDef("zeros"):
    @Phylanx
    def zeros(shape,dtype):
        return constant(0,shape,dtype)

a = zeros([3,3],dtype="float64") # call numpy zeros
a2 = zeros_phylanx([3,3],dtype="float64") # call phylanx zeros

@Phylanx
def foo():
    a = zeros([3,3],dtype="float64") # call phylanx zeros

Also add is_python() to allow routines to write code that evaluates differently inside or outside phylanx.