Java/C# std::vector<bool> workarounds for clang

Workaround clang++ 9.1.0 error not knowing std::vector<bool>::const_reference
is actually typedef to bool:

  li_std_vector_wrap.cxx:1838:40: error: no matching constructor for initialization of 'std::vector<bool>::const_reference'

Workaround is use

  const value_type& getitem(int index) throw (std::out_of_range) { ...
  // bool specialization:
  bool getitem(int index) throw (std::out_of_range) { ...

instead of

  const_reference_type getitem(int index) throw (std::out_of_range) { ...

Although the following would be better, it would require a more
complicated implementation:

  const_reference_type getitem(int index) throw (std::out_of_range) { ...
  // bool specialization:
  bool getitem(int index) throw (std::out_of_range) { ...

Lib/csharp/std_vector.i

@@ -233,7 +233,7 @@
         else
           throw std::out_of_range("index");
       }
-      const_reference getitem(int index) throw (std::out_of_range) {
+      CONST_REFERENCE getitem(int index) throw (std::out_of_range) {
         if (index>=0 && index<(int)$self->size())
           return (*$self)[index];
         else