cl/gcc-adapt-ext: Basic tests and support for C++ namespaced added.

This includes one dummy test #06, which should be completed when C++11
support will be implemented.
cl/gcc-adapt-ext: C++ using declaration tests added.

NOTE: Using declaration test #03 has been added for future use.
      It should be run after the tests for 'struct', 'union' and
      'class' namespaces has been added and properly tested.
cl/gcc-adapt-ext: C++ using directive & namespace alias tests added.
cl/gcc-adapt-ext: Removed unused variables in get_decl_scope().

These were leftovers of previous implementation testing.
cl/gcc-adapt-ext: Workaround to avoid SIGTRAP after handling METHOD_TYPE.

- probably temporary solution only
- provided-by: Kamil Dudka
cl/gcc-adapt-ext: Basic support for constructors & destructors added.

NOTE: This is actually support for processing of METHOD_TYPE node, which
      might change in future. The RECORD_TYPE node is still unhandled.
cl/gcc-adapt-ext: Namespace tests added to CL's test-suite.

NOTE: Support for namespaces should be completed now.
Merge branch 'extension/namespace-support' into cl/gcc-adapt-ext