To enable parsing constants more efficiently, mp_parse should be allowed
to raise an exception, and mp_compile can already raise a MemoryError.
So these functions need to be protected by an nlr push/pop block.
This patch adds that feature in all places. This allows to simplify how
mp_parse and mp_compile are called: they now raise an exception if they
have an error and so explicit checking is not needed anymore.
This enables proper interfacing with underlying OS - MicroPython doesn't
run the main loop, OS does, MicroPython just gets called when some event
takes place.
This patch consolidates all global variables in py/ core into one place,
in a global structure. Root pointers are all located together to make
GC tracing easier and more efficient.
Some rodata items can go in iram/irom segment, but not others. With
this patch ESP now has 24256 bytes of heap ram. It passes 228 out of
248 tests from tests/basics directory.
