Add support for arrays as port-types

[erlingrj]

Currently:

reactor R{
  output out: int[10]
}

is not supported, you have to do:

preamble {=
  typedef struct {
    int buf[10]
  } Array;
=}

reactor R {
  output out: Array
}

While it is acceptable to require typedef'ing a struct or a just a plain typdef, it would be nicer if we could just allow arrays