- refactoring
- renaming of error messages
- added canBusMode strings
- canSendMessage
  - implemented check on canBusMode (current status) before sending
    - in case of an error (disabled, bus off, error passive) subsequent transmit are ignored until bus mode has been reset to "undefined"
      - which happens automatically by the can timer mechanism 
	within canBusStateResetInterval_seconds with a granularity 
	of the calculated canTimerInterval given by CANTCON
- new: canSetCanTimer 
  - enables to set the can timer clock cycle either 
    - by setting the prescaler [0,0xff] Tclk = 1/F_CPU x 8 x (prescaler + 1)
    - or by
    - setting the time in seconds
- canInit
  - added canSetCanTimer
  - setting canBusStoreState 
- canIsGeneralStatusErrorAndAcknowledge
  moved as inline to can.h 
- canIsMObErrorAndAcknowledge
  moved as inline to can.h 
- ISR(CANIT_vect)
  - setting canBusStoreState for BOFFIT interrupt
- ISR(OVRIT_vect)
  - reset error canBusStoredStates every canBusStateResetInterval_seconds 
    with the granularity canBusStoredState of the calculated canTimerInterval given by CANTCON 
    to canBusStoredState to undefined to allow for recovery

  - defined macro CAN_BUS_STATE_RESET_INTERVAL_SECONDS = 60.
  - enum:
      - bus state 
      - timer units 
  - new inline canGetCurrentBusModeStatus 


git-svn-id: https://subversion.gsi.de/epics/trunk/hadcon/API-Slave@408 50339f28-a4cd-11e1-ab1f-8360dde1fe65