py: Fix compile of class with keyword arguments in bases.
py: More output in showbc.
Add staticmethod and classmethod to builtin namespace.
Implement fixed buffer vstrs; use them for import path.
py: Put builtins into ROM table.

Linear table at the moment, to eventually be replaced with a hash table
generated by a preprocessor.

Dynamic table is retained so that builtins can be overridden.
stm: Mount SD card on 1:/ if present.

If SD card is present on (soft) reset then it's mounted on 1:/ and files
can be openned using, eg, open('1:/test.txt', 'r'), or 'w' for writing.
Make mp_obj_str_get_data return char* instead of byte*.

Can't decide which is better for string type, char or byte pointer.
Changing to char removes a few casts.  Really need to do proper unicode.
py: Allow mp_map_t to be initialised by a fixed-size, const table.

This allows keyword maps to be created directly from stack data.
py: Pass keyword args to native functions by using the stack.

Passing keyword arguments to a native function now no longer requires
heap memory.  The kw_args map is created on the stack using the args
array as the table.
py: Add some qstrs to the global table.
Rename "rawsocket" module to "microsocket".

It's no longer intended to provide just "raw" socket interface, may include
some convenience methods for compatibility with CPython socket - but anyway
just minimal set required to deal with socket client and servers, not wider
network functionality.
io.File, socket types: Add fileno() method.

Implementation is duplicated, but tolerate this for now, because there's
no clear idea how to de-dup it.
ffi: Fix mp_obj_str_get_data() return type.
unix microsocket: Add dummy makefile() method.

Unlike CPython socket, microsocket object already implements stream protocol
(read/write methods), so makefile() just returns object itself. TODO: this
doesn't take care of arguments CPython's makefile() may accept.
Refactor list comparison code to mp_seq_cmp_objs().
Implement tuple comparison.
Implement tuple addition.
Implement tuple multiplication.
unix: Implement time.sleep().
Add NotImplementedError.