(maint) Add the behavior for count() with arrays and hashes

(maint) Add the behavior for count() with arrays and hashes

Without this patch the expected behavior of the count() function when
dealing with an out of bound array index and with a hash key that does
not exist is implicitly encoded in the spec examples.  This is a problem
because the expected behavior is not clear for something similar to the
following example:

    node default {
      $ary = [ 1, 2, 3 ]
      $ary_undef = $ary[100]
      $hsh = { 'one' => 1 }
      $hsh_undef = $hsh['dne']
      $count = count(['hi', $ary_undef, $hsh_undef])
      notice "Count is ${count}"
    }

This patch addresses the problem by making the expected behavior
explicit in the examples.