This makes unix "uselect" compatible with baremetal "uselect". Previosuly,
unix version accepted file/socket objects, but internally converted that
to file descriptors, and that's what .poll() returned. To acheive new
behavior, file-like objects are stored internally in an array, in addition
to existing array of struct pollfd. This array is created only on first
case of file-like object being passed to .register(). If only raw fd's are
passed, there will be no additional memory used comparing to the original
implementation.
Implementations of persistent-code reader are provided for POSIX systems
and systems using FatFS. Macros to use these are MICROPY_READER_POSIX and
MICROPY_READER_FATFS respectively. If an alternative implementation is
needed then a port can define the function mp_reader_new_file.
Its addition was due to an early exploration on how to add CPython-like
stream interface. It's clear that it's not needed and just takes up
bytes in all ports.
Now, to use frozen bytecode all a port needs to do is define
FROZEN_MPY_DIR to the directory containing the .py files to freeze, and
define MICROPY_MODULE_FROZEN_MPY and MICROPY_QSTR_EXTRA_POOL.
To make its inclusion as frozen modules in multiple ports less magic.
Ports are just expected to symlink 2 files into their scripts/modules
subdirs.
Unix port updated to use this and in general follow frozen modules setup
tested and tried on baremetal ports, where there's "scripts" predefined
dir (overridable with FROZEN_DIR make var), and a user just drops Python
files there.
It's implemented in terms of usleep(), and POSIX doesn't guarantee that
usleep() can sleep for more than a second. This restriction unlikely
applies to any real-world system, but...
In order to have more fine-grained control over how builtin functions are
constructed, the MP_DECLARE_CONST_FUN_OBJ macros are made more specific,
with suffix of _0, _1, _2, _3, _VAR, _VAR_BETEEN or _KW. These names now
match the MP_DEFINE_CONST_FUN_OBJ macros.
Now there is just one function to allocate a new vstr, namely vstr_new
(in addition to vstr_init etc). The caller of this function should know
what initial size to allocate for the buffer, or at least have some policy
or config option, instead of leaving it to a default (as it was before).
