Add std::unique support

Simple copy of current auto_ptr support (just suppport for
functions returning std::unique_ptr).

Closes #1722

Examples/test-suite/ruby/cpp11_std_unique_ptr_runme.rb

@@ -0,0 +1,27 @@
+#!/usr/bin/env ruby
+
+require 'swig_assert'
+
+require 'cpp11_std_unique_ptr'
+
+def gc_check(expected_count)
+#  GC.start(full_mark: true, immediate_sweep: true)
+  GC.start
+# GC is not reliably run, skip check
+#  swig_assert_equal_simple(expected_count, Cpp11_std_unique_ptr::Klass::getTotal_count())
+end
+
+k1 = Cpp11_std_unique_ptr::makeKlassUniquePtr("first")
+k2 = Cpp11_std_unique_ptr::makeKlassUniquePtr("second")
+swig_assert_equal_simple(2, Cpp11_std_unique_ptr::Klass::getTotal_count())
+
+gc_check(2)
+k1 = nil
+gc_check(1)
+
+swig_assert_equal_simple(k2.getLabel(), "second")
+gc_check(1)
+
+k2 = nil
+gc_check(0)
+