The frozen module `_boot.py` was not being loaded on restart
because `pyexec_frozen_module()` did not know about the new `.frozen`
pseudo-directory. Updated lower-level routine to look in the right place.
Also made ".frozen" and related values be `#define`s.
This introduces a skip_if module that can be used by tests to
determine when they should be skipped due to the environment.
Some tests have been split in order to have finer grained skip
control.
This makes it clear when frozen modules are loaded as opposed to the empty path
which represents the current working directory. Furthermore, by splitting the two
apart this allows one to control in what order frozen modules are loaded.
This is a prerequisite for #56.
The with semantics of this function is close to
pkg_resources.resource_stream() function from setuptools, which
is the canonical way to access non-source files belonging to a package
(resources), regardless of what medium the package uses (e.g. individual
source files vs zip archive). In the case of MicroPython, this function
allows to access resources which are frozen into the executable, besides
accessing resources in the file system.
This is initial stage of the implementation, which actually doesn't
implement "package" part of the semantics, just accesses frozen resources
from "root", or filesystem resource - from current dir.
Now frozen modules is treated just as a kind of VFS, and all operations
performed on it correspond to operations on normal filesystem. This allows
to support packages properly, and potentially also data files.
This change also have changes to rework frozen bytecode modules support to
use the same framework, but it's not finished (and actually may not work,
as older adhox handling of any type of frozen modules is removed).
The config variable MICROPY_MODULE_FROZEN is now made of two separate
parts: MICROPY_MODULE_FROZEN_STR and MICROPY_MODULE_FROZEN_MPY. This
allows to have none, either or both of frozen strings and frozen mpy
files (aka frozen bytecode).