Every 4294967295 milliseconds (2 ^ 32 - 1), system_millis will overflow.
This means that every 49.71 days, system_millis will reset to zero.
Comparisons like `system_millis < (system_millis + 1)` would fail if the
latter had overflown and the former had not.
This is non-critical because the worst case is that one second could be
skipped or the screen could lock early.
This poses no threat to the exponential backoff used for protection
against brute force.
Removed `usbDelay(uint32_t cycles)`, added `usbSleep(uint32_t millis)`
The same method signature could cause silent code breakage at runtime,
as opposed to noisy code breakage at compile time which is the better
kind.
This patch adds calls to usbPoll in the progress callback. This
should address #98.
We call usbDelay instead of Poll, to call usbd_poll several times.
Otherwise it would only handle one event instead of handling all
events that were pending so far. The ugly magic number 5 is a guess.
Note that we also need to set usbTiny, so that we don't recursively
process messages. Since we don't know whether usbTiny is set, we
need to store the old value (especially true for u2f).
This fix also relies on another fix in libopencm3.
Tested, see f41cbedd8becee05a830f418d13aa665125464547db5c7a6cd28f21639fe1228
and c9348040bbc2024e12dcb4a0b4806b0398646b91acf314da028c3f03dd0179fc
on testnet
New output scripts for segwit addresses in accordance to BIP-142 and BIP-141.
This allows Trezor to pay to segwit users, but it doesn't enable segwit for
Trezor itself.
Holding confirm button at home screen asks user whether they wish to
lock the TREZOR (clear the cached PIN and passphrase and show the
screensaver). This is identical behaviour to the ClearSession message.
