4bitle: return type of Send.cancel should be error_t

was uint8_t but should have been error_t to match the
interface of AMSend.cancel.
Expose the LowPowerListening interface in ActiveMessageC for platforms
where this was not yet done. The remaining platforms where this is not
exposed are: eyesIFX (Tda5250, LowPowerListening is not implemented) and
tinynode (XE1205, has special LPL component and interface).
Remove confusing default channel define from RFxxx register definitions (from Elena Chervakova)
Escape serial CRC, allow limited retries.
Merge pull request #169 from carlsondc/dc

Escape serial CRC, allow limited retries.
CC2420X driver fixes

pull request 173: fixed a critical race condition that caused the driver
to hang under high loads, restructured code to eliminate long atomic
sections
Merge branch 'master' into wserial
Support for low baudrate serial.
Support for Deluge.

The Wserial platform with non-power-of-two page size in AT45DB041D. (HplAt45db_chip.h: AT45_PAGE_SIZE = 264 and AT45_PAGE_SIZE_LOG2 = 9). Fix issue #144.
Other platform should be checked. If power-of-two page size is used (eg. OTP programmed see "13. 'Power of 2' Binary Page Size Option" in datasheet AT45DB041D) then "HplAt45db_chip.h" must be corrected (eg. HplAt45db_chip.h: AT45_PAGE_SIZE = 256 and AT45_PAGE_SIZE_LOG2 = 8).
The Tosboot use "Continuous Array Read (Low Frequency Mode: 03H): Up to 33 MHz" for reading instead of legacy and undocumented "Continuous Array Read 68H".