v2.0.0

1. Drop support for GCC-XML.

• Drop all the demangled name attributes

• Drop declarations.class_t.USE_DEMANGLED_AS_NAME

2. Drop support for Python 2.6, Python 2.7, Python 3.2, Python 3.3, Python 3.4.

3. Add support for Python 3.5, Python 3.6, Python 3.7, Python 3.8.

4. Deprecated all the i_depend_on_them methods from the declaration_t
   class hierarchy. Instead of using decl.i_depend_on_them(), please use the
   declarations.get_dependencies_from_decl(decl) function from the
   declarations module, which returns the same result.

5. Add support for -std=c++17 and -std=c++2a flags

6. Add g++ and gcc to better support gnu compilers on windows