Defined basic C API for the kernel.

- Just the API declarations to see what it would look like.
- No implementation.
Fully spelled out ‘semaphore’ in C API.
Defining more of the C version API.
Started converting code to C.

- More updates to C API.
- Created an ar_internal.h header.
- Started converting kernel and thread sources to C.
Lots of changes towards C API.
C API rewrite work: completed thread functions.

- Also improved list management functions.
C API rewrite work: list improvements, converted sem.

- Added ar_list_t type with add and remove helper methods for C++.
- Changed previous list heads to use ar_list_t type.
- Made thread block and unblock operations methods on ar_thread_t.
- Reworked names of list heads versus list nodes.
- Added missing name fields to most kernel object structs.
- Converted semaphore code.
C API rewrite work: finished conversion, got everything building.

- Added ar_timer.cpp to K60 test project.
- Added a couple more error codes.
- Added APIs to get names of all objects.
- Converted C++ classes to be lightweight wrappers over C API, but
  the same exact API is retained.
- Converted port files.
- Added timer sort predicate.
- Added checks for non-NULL object pointers to all APIs.
- Convered mutex, queue, and timer sources.
- Implemented C APIs to get values of objects, like thread state.
- Updated basic_test.cpp so it will compile.
- Various other cleanup and changes.
Fixing bugs in C implementation.

- Enabled global object lists and fixed a couple related bugs.
- Got virtual thread entry point working for Ar::Thread, though it could
  be made simpler.
- Added a reference pointer field to ar_thread_t, used to point back
  to the Ar::Thread instance.
- Made Ar::Thread::getCurrent() use the new ref field to get the Thread
  instance from an ar_thread_t.
- A few other minor changes.
- Added an item to the todo list.
Renamed public includes for Argon.

- Added an argon.h header that include both the C and C++ APIs.
- Wrapped C++ API so it will be ignored by a C compiler.
- Updated include directives in test code.
Merge branch 'dev_c_api'

* dev_c_api:
  Renamed public includes for Argon.
  Fixing bugs in C implementation.
  C API rewrite work: finished conversion, got everything building.
  C API rewrite work: list improvements, converted sem.
  C API rewrite work: completed thread functions.
  Lots of changes towards C API.
  Started converting code to C.
  Defining more of the C version API.
  Fully spelled out ‘semaphore’ in C API.
  Defined basic C API for the kernel.