State that this doc describes generic, "core" MicroPython functionality,
any particular port may diverge in both directions, by both omitting
some functionality, and adding more, both cases described outside the
generic documentation.
Describe that the only portable way to deal with addresses is by using
getaddrinfo(). Describe that some ports may support tuple addresses using
"socket" module (vs "usocket" of native MicroPython).
This clarifies return values and the handling of invalid (e.g. newline)
characters.
Encoding conforms to RFC 3548, but decoding does not, as it ignores invalid
characters in base64 input. Instead, it conforms to MIME handling of base64
(RFC 2045).
Note that CPython doesn't document handling of invalid characters in
a2b_base64() docs:
https://docs.python.org/3/library/binascii.html#binascii.a2b_base64 , so
we specify it more explicitly than it, based on CPython's actual behavior
(with which MicroPython now compliant).
This makes top-level ToC of the pyboard docs consistent with other ports
(consisting of 3 chapters: QuickRef, General Info, and Tutorial).
Also, some other minor tweaks applied, like local ToC for General Info and
headings mentioning pyboard.
This pseudo-section causes artifacts with latexpdf generation (almost
empty page with list containing literal "genindex", "modeindex", "search"
items). For HTML docs, these sections can be accessed from "home" page.
We don't use alpha/beta/RC, so for us version and release should be the
same, or it leads to confusion (for example, current, 1.9.1 docs are
marked as 1.9 at places).