Use flatbuffer unique_ptr instead of std's.

Stlport does not have std unique_ptr, so using the one provided by
flatbuffers.
Also fixing a problem with the flatbuffer unique_ptr, and a test.

include/flatbuffers/idl.h

@@ -284,7 +284,7 @@ struct StructDef : public Definition {
   size_t minalign;  // What the whole object needs to be aligned to.
   size_t bytesize;  // Size if fixed.
 
-  std::unique_ptr<std::string> original_location;
+  flatbuffers::unique_ptr<std::string> original_location;
 };
 
 inline bool IsStruct(const Type &type) {

include/flatbuffers/stl_emulation.h

@@ -170,7 +170,7 @@ inline void vector_emplace_back(std::vector<T> *vector, V &&data) {
       return *this;
     }
 
-    const T& operator*() const { return ptr_; }
+    const T& operator*() const { return *ptr_; }
     T* operator->() const { return ptr_; }
     T* get() const noexcept { return ptr_; }
     explicit operator bool() const { return ptr_ != nullptr; }

tests/test.cpp

@@ -1661,7 +1661,7 @@ void FlexBuffersTest() {
       int ints[] = { 1, 2, 3 };
       slb2.Vector("bar", ints, 3);
       slb2.FixedTypedVector("bar3", ints, 3);
-      slb.Bool("bool", true);
+      slb2.Bool("bool", true);
       slb2.Double("foo", 100);
       slb2.Map("mymap", [](flexbuffers::Builder& slb3) {
         slb3.String("foo", "Fred");  // Testing key and string reuse.