intppty set interface argument passing properties

## Syntax

    funs=intppty()
                intppty(fun)
                intppty(fun, action)

## Arguments

fun

  string, module name (see getmodules)

action

  string, action to realize, value should be "add" or "remove"

funs

  string vector, vector of module names (see getmodules)

## Description

The interface programs may be written in 2 different ways for the mode of function argument passing.

In the first and default way, the arguments are passed by value. With the following syntax:

    foo(A,1+2)

the argument associated with `A` will be passed by value (a copy of `A` is made before `foo` is called), and the argument associated with `1+2` will be passed by value.

In the second way arguments may be passed be reference if there are "named arguments" (no copy of the variable value is done). With the following syntax:

    foo(A,1+2)

the argument associated with `A` will be passed by reference, and the argument associated with `1+2` will be passed by value.

Warning: declaring that the interface with number `fun` can handle arguments passed by reference if it is not the case should produce unpredictable results.

`intppty(fun, "remove")` suppress this property for the interface `fun`.

`intppty()` returns the vector of interfaces which handle arguments passed by reference.

This function may be useful for dynamically loaded interface (see addinter).

## See also

- getmodules
- addinter