heapq: Convert __about__ to "second docstring".

So it can be discarded.
make_metadata.py: Support comments.
heapq: Switch to metadata.txt.
glob: Explicitly import os.path.
make_metadata.py: Remove current dir from sys.path.

Otherwise MicroPython will pick up glob as an empty namespace package from
the current dir otherwise.
re-pcre: sub(): If suffix of string matched, None was returned.
make_metadata.py: Allow to have module name != distribution name.

Like, micropython-re-pcre hosts re.py.
http.client: Add pristine from CPython 3.3.3.
http.client: Explicitly check for str type instead of "encode" method.

MicroPython string type shares setup with bytes, and thus both have entries
for "encode" and "decode" (but only one valid for a type really works).
http.client: Comment out io.RawIOBase, as uPy lacks complete io hierarchy.
http.client: Add basic example.
http.client: Add metadata.
os: Add urandom().
re-pcre: Implement count arg to re.sub().
functools: Add dummy update_wrapper(), wraps().
sqlite3: Add .close() methods, better error checking and reporting.
sqlite3: Add params args for execute() method.
sqlite3: Auto-execute non-select statements in execute().
os: Add name, environ vars (last - as dummy).
Add a basic docs as a stopgap measure against user confusion.

TODO: elaborate.