Add unittest support for ATOMIC_BLOCK
- BASEPRI emulation on UNIT_TEST target
- documentation cleanup / fixed missspelings
- ATOMIC_BARRIER implemented for CLang, using blocks
- ATOMIC_BARRIER is using macros to separate barriers
gcc specific unittest for ATOMIC_BARRIER
ATOMIC_BARRIER clang unittest
quick hack to enable CLangs -flocks + ATOMIC_BARRIER tests
Needs cleanup
* Enable test
* Add libBlocksRuntime dependency to Travis
