Fix type inferencing, syntax highlighting and code navigation for variadic category methods

[eric-milles]

Consider the following (derived from GROOVY-5609):

class Cat {
  static <T> void foo(List<T> self, T[] tees) {
  }
  static <T> void foo(T[] self, T[] tees) {
  }
}

use (Cat) {
  Integer[] array = [1,2,3]
  array.foo(array)
  array.foo(4,5,6)
  array.foo(4)
  array.foo()

  List<Integer> list = [1,2,3]
  list.foo(array)
  list.foo(4,5,6)
  list.foo(4)
  list.foo()
}

The calls with arguments not matching the number of parameters are not being recognized.

[eric-milles]