ASTL (Android STL) is a slimmed-down version of the regular C++ STL.

Its sole purpose for existence is to be able to compile some third party
packages. As a result only a subset of the regular STL is provided. We only add
feature to it as we need them.

Size of the library is a concern. For that reason, template usage has been
reduced to a bare minimum, there is little parametrization in classes.

To keep things simple, some inheritance hierarchies are just not there (e.g
string is not a template specialization of basic_string - there is no
basic_string class template.)