Prototype for dot operator

[Martin Sjölund]

Implement a dot operator prototype (disabled for +std=3.3 and below), like ​m:#1512 suggests (only for function calls).

function f
  input Real r;
  output Real x=1,y=2;
end f;

function y
  input Real i;
  output Real o = f(i).y;
end y;

function x
  input Real i;
  output Real o = f(i).x;
end x;

model M
  constant Real r1 = y(1.5);
  constant Real r2 = x(1.5);
end M;

[Martin Sjölund]

Fixed in r24168.