Add G-Watch to preload

See merge request !396

The button to turn on the LEDs gets pressed easily, making them waste
battery.

This reduces the power consumption when the display is off by
about 3.8 mA.

card10 with BLE off and without this patch: 11.5 mA
card10 with BLE off and with this patch: 7.7 mA

Read date/time from iOS device

See merge request !406

Accessory Design Guidelines for Apple Devices says that TX power should
be included in the advertisement.

Also ask for the current time service in the scan report so the card10
shows up in the system dialog.

See merge request !405

See merge request !404

fix(ble): Use the term "pairing" in the UI

See merge request !403

See merge request !402

User study: https://twitter.com/schne1der_/status/1310698476108476418

Assorted fixes/cleanups

See merge request !401

Use CSPRNG for BTLE

See merge request !400

I don't trust the TRNG/PRNG combo inside the binary blob.

See merge request !399

The linker should already catch this case and error out early but just
to be absolutely sure, add a second check here so we don't get an
unexpectedly large epicardium binary which would overlap into pycardium
storage.

Signed-off-by: Rahix <rahix@rahix.de>

Hawkmoth is not yet working with Spinx 3; issue a warning when detecting
a Sphinx 3 environment as the resulting docs will be broken.

Signed-off-by: Rahix <rahix@rahix.de>

The tr hack we used so far has been painful.  The amount of locale
environment variables we need to set is surely a telling sign of that ...

Replace this with objcopy which can do the same thing, but much easier
and without locale related side effects ;)

Signed-off-by: Rahix <rahix@rahix.de>

Disable these warnings as they don't really help in our case:

    In file included from ../epicardium/modules/config.c:8:
    ../epicardium/modules/config.c: In function 'trim':
    ../epicardium/modules/config.c:133:28: warning: array subscript has type 'char' [-Wchar-subscripts]
      133 |  while (*start && !isgraph(*start))
          |                            ^~~~~~
    ../epicardium/modules/config.c:138:27: warning: array subscript has type 'char' [-Wchar-subscripts]
      138 |   while (*end && !isgraph(*end))
          |                           ^~~~
    ../epicardium/modules/config.c: In function 'epic_config_get_string':
    ../epicardium/modules/config.c:335:26: warning: array subscript has type 'char' [-Wchar-subscripts]
      335 |  while (*end && !iscntrl(*end))
          |                          ^~~~
    ../epicardium/modules/config.c: In function 'epic_config_set_string':
    ../epicardium/modules/config.c:519:28: warning: array subscript has type 'char' [-Wchar-subscripts]
      519 |   while (*end && (!iscntrl(*end) || isblank(*end)))
          |

Signed-off-by: Rahix <rahix@rahix.de>

See merge request !394