For make v3.81, using "make -B" can set $? to empty and in this case the
auto-qstr generation needs to pass all args (ie $^) to cpp.  The previous
fix for this (which was removed in 23a693ec)
used if statements in the shell command, which gave very long lines that
didn't work on certain systems (eg cygwin).

The fix in this patch is to use an $if(...) expression, which will evaluate
to $? (only newer prerequisites) if it's non empty, otherwise it will use
$^ (all prerequisites).

These tests excercise cases that are fixed by the previous two commits.

Previous to this patch the mp_emit_bc_adjust_stack_size function would
adjust the current stack size but would not increase the maximum stack size
if the current size went above it.  This meant that certain Python code
(eg a try-finally block with no statements inside it) would not have enough
Python stack allocated to it.

This patch fixes the problem by always checking if the current stack size
goes above the maximum, and adjusting the latter if it does.

This patch fixes a regression introduced by
088740ec

This patch fixes a regression introduced by
71a3d6ec

Previous to this patch the n_state variable was referring to that computed
at the very start of the mp_execute_bytecode function.  This patch fixes it
so that n_state is recomputed when the code_state changes.

For consistent Pin/Signal class hierarchy. With it, Signal is a proper
(while still ducktyped) subclass of a Pin, and any (direct) usage of Pin
can be replace with Signal.

As stmhal's class is reused both as machine.Pin and legacy pyb.Pin,
high/low methods actually retained there.

Both aren't part of generic Hardware API: It's impossible to implement
.id() method in a generic case (e.g., when Pin is instantiated by the
underlying OS/RTOS). .board attribute is an obvious space hog which
instead can be implemented on Python level if needed.

It's not part of MicroPython HW API and can be easily implemented on Python
level in case of need.

Saved 56 bytes of binary.

Returns 0 or 1, corresponding to no or at least 1 char waiting.

The docs are updated and describe the new behaviour of these methods.

Following finalized naming in uasyncio.

If no network driver is enabled (e.g., it doesn't exist for a particular
board), it will be NULL.

Instead, just peek a packet at the head of the queue and work with it.

Here we wait for non-empty FIFO, and then directly access/drop its head
element.

Regression was introduced by ec534609

pyb.UART has a superset of machine.UART functionality so can be used to
provide compatibility with other ports that also implement machine.UART.

Existing code failed if seek() went past EOF (which is acceptable when writing).

To make them harder to miss.

May be a port-specific method, not portable, not part of the official
specification.

Working on a build with PY_IO enabled (for PY_UJSON support) but PY_SYS_STDFILES disabled (no filesystem).  There are multiple references to mp_sys_stdout_obj that should only be enabled if both PY_IO and PY_SYS_STDFILES are enabled.

This solves a case when socker_read() has blocked on fifo, and then peer
closed event arrives.