mbed.h has 'using namespace mbed;', hence some of the files skip
adding required namespace to the code, it is always good to specify the
namespace around the elements in header and `using namespace` in
specific CPP files, instead of all
Nanostack related files moved under 'feature/nanostack'
Common libraries moved to 'features/frameworks'
Allow FEATURE_COMMON_PAL still to be defined in the build so
that we don't break any builds.