objtype: Implement basic framework for subclassing native types.

This implements checking of base types, allocation and basic initialization,
and optimized support for special method lookups. Other features are not yet
supported.
tests: Add basic tests for subclassing native types and using special methods.

Even of these, some features do not yet work as expected.
objtype: Add support for looking up non-method attrs in native base class.
tests: Add test for accessing attribute of inherited native type.
objtype: Support calling normal methods inherited from native base class.

Biggest part of this support is refactoring mp_obj_class_lookup() to return
standard "bound member" pair (mp_obj_t[2]). Actual support of inherited
native methods is 3 lines then. Some inherited features may be not supported
yet (e.g. native class methods, native properties, etc., etc.). There may
be opportunities for further optimization too.
tests: Add test for calling inherited native method on subclass.
stmhal: Make LED.intensity return the same value it was set to.

Also give proper error message when trying to construct a non-existent
LED.

Addresses issue #530.
stmhal: Reinstate CC3000 driver from old stm/ port.

It's not enabled by default because it doesn't fully work.  It can
connect to an AP, get an IP address and do a host-lookup, but not yet do
send or recv on a socket.
Merge pull request #528 from pfalcon/native-subclass1

Initial support for subclassing native types
stmhal, docs: Small changes to URL links; adds list of files if none given.

This documentation is now available at micropython.org/doc/
Merge branch 'master' of github.com:micropython/micropython
objfun: Add function name accessor and .print slot method.
py: Add tentative scheme for error messages configuration.
Add flashboard target to the stmhal Makefile to run dfu-util

Which allows you to run "make -C stmhal flashboard" from the top-level directory.
Also ties in nicely with my configurable BUILD directory from #506
Fix pin initialization when a mode argument is provided
Fix the builtin min() and max() functions (and add tests).
Fixes #539
objgenerator: .print(): Output real underlying function name.
objgenerator: Fix check for too few args passed to gen function.
objfun: More debug logging.
Merge pull request #544 from lurch/fix-minmax

Fix the builtin min() and max() functions (and add tests).