resolve Hash.cpp compile error on Android

Resolves these errors on Android:

```
Error: hxcpp/src/hx/Hash.cpp: In member function 'virtual void hx::IntHash::__Mark(hx::MarkContext*)':
hxcpp/src/hx/Hash.cpp:192: error: using 'typename' outside of template
hxcpp/src/hx/Hash.cpp:192: error: using 'typename' outside of template
hxcpp/src/hx/Hash.cpp: In member function 'virtual void hx::IntHash::__Visit(hx::VisitContext*)':
hxcpp/src/hx/Hash.cpp:204: error: using 'typename' outside of template
hxcpp/src/hx/Hash.cpp:204: error: using 'typename' outside of template
```