This is to keep the top-level directory clean, to make it clear what is
core and what is a port, and to allow the repository to grow with new ports
in a sustainable way.
Previously they used historical "pyb" affix causing confusion and
inconsistency (there's no "pyb" module in modern ports; but people
took esp8266 port as an example, and "pyb" naming kept proliferating,
while other people complained that source structure is not clear).
Move definition of mp_builtin_open_obj to a separate module, then file.c
becomes more or less compartmentalized FatFs file class, which can be used
together with file class implementations for other (V)FSes.
Blanket wide to all .c and .h files. Some files originating from ST are
difficult to deal with (license wise) so it was left out of those.
Also merged modpyb.h, modos.h, modstm.h and modtime.h in stmhal/.
Damien George
Paul Sokolovsky