Implicit function search and Fortran calls

This version supports implicit function search. Instead of

f = lib.find_function("myfunc")
f.args_type("char *", "int")
req = f(ctxt, "abc", 15)

now you can do:

lib.myfunc.args_type("char *", "int")
req = lib.myfunc(ctxt, "abc", 15)

OnStack() now works with any variables that support the buffer protocol, so now numpy arrays can be passed on stack (IN, INOUT, OUT) to fortran VE function.

The module can be installed from PYPI, also in virtualenvs:

pip install py-veo