vstr is initially intended to deal with arbitrary-length strings. By
providing a bit lower-level API calls, it will be also useful to deal
with arbitrary-length I/O buffers (the difference from strings is that
buffers are filled from "outside", via I/O).

Another issue, especially aggravated by I/O buffer use, is alloc size
vs actual size length. If allocated 1Mb for buffer, but actually
read 1 byte, we don't want to keep rest of 1Mb be locked by this I/O
result, but rather return it to heap ASAP ("shrink" buffer before passing
it to qstr_from_str_take()).

By dispatching to long int methods.

Added public domain implementations of strchr and strstr.

Initialize is_kw for dynamically allocated mp_obj_fun_native_t ojects.

This should fix issue #171

Also new vector_log png with alpha

Implement a basic str.find; fixes #67

Elaborate small-int/long-int

Set features. As per #143.

Added a hacky implementation for %g

See pyb_usart_global_debug variable.

Also did some work on USB OTG, but nothing working yet.

Long int is something which doesn't fit into SMALL_INT partion of
machine_int_t. But it's also something which doesn't fit into
machine_int_t in the first place.

We likely should make mp_obj_new_int() inline, and rely on its
encapsulated check rather than inline checks everywhere explicitly.

Also, parser for big small int values is still broken.

Small graphic - Useful for WebBanners, etc...

Implement type virtual equality method support and implement comparisons for lists

Added memzip filesystem support for teensy