This allows calls to `allocate_memory()` while the VM is running, it will then allocate from the GC heap (unless there is a suitable hole among the supervisor allocations), and when the VM exits and the GC heap is freed, the allocation will be moved to the bottom of the former GC heap and transformed into a proper supervisor allocation. Existing movable allocations will also be moved to defragment the supervisor heap and ensure that the next VM run gets as much memory as possible for the GC heap.
By itself this breaks terminalio because it violates the assumption that supervisor_display_move_memory() still has access to an undisturbed heap to copy the tilegrid from. It will work in many cases, but if you're unlucky you will get garbled terminal contents after exiting from the vm run that created the display. This will be fixed in the following commit, which is separate to simplify review.
When a TLS connection is closed by the server it usually sends a
notice. We see this incoming byte with lwip_ioctl and try to read
it. The read returns 0 but we keep trying anyway. Now, we quit
trying when we get zero back. If the connection was still alive
it'd either read a byte or delay until a byte could be read.
While trying to debug #3572, I noticed that I would frequently break in
the midst of gettimeofday and that the routine get_adjusted_boot_time
had to take and release locks. Furthermore, we don't want "adjusted"
boot time, which could go forwards or backwards depending on the
adjustment (such as setting the clock used by gettimeofday() to the network
time)
Before, there were two problems:
* Even if a pulsein was never constructed, supervisor_disable_tick
would occur during restart. This could cancel out a supervisor_enable_tick
from someplace else, with unexpected results.
* If two or more pulseins were constructed, each one would enable ticks,
but only the last one deinited (or the reset routine) would disable,
leaving ticks running indefinitely.
In my testing, it seemed that this led to the board sometimes stopping when
it should have auto-reloaded.
