generic error in Resource/ResourceConfigure interaction

ResourceConfigure is called outside atomic.

fix issue #164
arbitration futher fixes
msp430: tweak msp430hardware, better explanation of MSP430_HAS_I2C.
Merge branch 'arbitration-configure-fix'
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).