Work around differences in clang libc++ std::vector<bool>::const_reference

clang++ using -stdlib=libc++ defines const_reference as a class,
to map boolean vectors onto a bit set.  Because swig does
not "see" the type as "const &" it generates incorrect code for this case,
generating a declaration like:

  const_reference result;

When const_reference is a typedef to 'bool' as is the case with stdlibc++
this works.  When this is actually a constant reference, this is clearly
invalid since it is not initialized.  For libc++, this is a class
which cannot be default constructed, resulting in an error.  The fix
is to explicitly define the various accessor extensions as having a
bool return type for this specialization.

Lib/java/std_vector.i

@@ -61,7 +61,7 @@ namespace std {
         %rename(add) push_back;
         void push_back(const value_type& x);
         %extend {
-            const_reference get(int i) throw (std::out_of_range) {
+            bool get(int i) throw (std::out_of_range) {
                 int size = int(self->size());
                 if (i>=0 && i<size)
                     return (*self)[i];