Allow usage of polymorphic types as functional inputs

[Per Östlund]

It would be nice if this would work:

function f1<PF>
  input Real x;
  input PF pf;
  output Real y = pf(x);
end f1;

function f2
  input Real x;
  input Real y = 2.0;
  output Real z = x + y;
end f2;

model test
  Real x = f1(3.0, f2);
end test;

Currently the compiler complains that f1.pf is a component and not a type, but in this case it would be both. Allowing this would remove the need to declare partial functions everywhere when using functions as arguments.

[Martin Sjölund]

The problem is that you get no information about what kind of type PF is. When the type interface is generated, algorithm sections and bindings are removed. So you cannot type-check this when doing separate compilation.