Previously they used historical "pyb" affix causing confusion and
inconsistency (there's no "pyb" module in modern ports; but people
took esp8266 port as an example, and "pyb" naming kept proliferating,
while other people complained that source structure is not clear).

As we're looking towards adding OTA support, calculation of a FlashROM
area which can be used for filesystem (etc.) may become complex, so
introduce C function for that. So far it just hardcodes current value,
0x90000. In the future the function may be extended (and renamed) to
return the size of area too.

To save iRAM.

One can instead lookup __name__ in the modules dict to get the value.

Requires firmware generated by the latest makeimg.py (which stores size
and md5 of the firmware together with the firmware itself).

By design, at wake up from deepsleep, the RTC timer will be reset, but
the data stored in RTC memory will not [1]. Therefore, we have to adjust
delta in RTC memory before going into deepsleep to get almost correct
time after waking up.

[1] http://bbs.espressif.com/viewtopic.php?t=1184#p4082

Exposed as esp.dht_readinto.  Probably should go somewhere less
port-specific.

APA102 is a new "smart LED", similar to WS2812 aka "Neopixel".

These symbols are still defined in terms of the system Exxx symbols, and
can be switched to internal numeric definitions at a later stage.

Note that extmod/modlwip still uses many system Exxx symbols.

Useful for testing fragmentation issues in OS heap. E.g. freemem() may
report large amount, but is it possible to actually allocate block of
a given size? Issue malloc() (followed by free()) to find out.

Return number of free inernal WiFi buffers.

All functionality of the pyb module is available in other modules, like
time, machine and os.  The only outstanding function, info(), is
(temporarily) moved to the esp module and the pyb module is removed.

They almost certainly needed by any C code which calls Python callbacks.

Returns FlashROM size in bytes from vendor SDK's point of view, not
physical size.

They call into vendor SDK functions system_get_free_heap_size() and
system_print_meminfo() respectively.

Use esp.osdebug(None) to disable, or esp.osdebug(uart_id) to send output
to a UART.

Using https://github.com/pfalcon/esp-open-lwip project.

The first argument to the type.make_new method is naturally a uPy type,
and all uses of this argument cast it directly to a pointer to a type
structure.  So it makes sense to just have it a pointer to a type from
the very beginning (and a const pointer at that).  This patch makes
such a change, and removes all unnecessary casting to/from mp_obj_t.

Based on vendor API documentation, untested on real hardware.

py/mphal.h contains declarations for generic mp_hal_XXX functions, such
as stdio and delay/ticks, which ports should provide definitions for.  A
port will also provide mphalport.h with further HAL declarations.

TODO: Contributed code in modesp incorrectly uses private gc_* API.

esp8266: Changed esp_scan to keep the current WiFi operating mode but throw an exception if WiFi is in AP only mode