add sha256 implementation
Eliminate multiline macros, embrace C99
Fix byteorder problems
added doxygen doc to sha256
add a barrier for msba2 due to wrong results
Merge pull request #96 from mehlis/sha256

add sha256 implementation
add missing include for mutex
use std include style
remove unused static function
Merge pull request #122 from mehlis/hwtimer-fixes

Hwtimer fixes