RS lib: fix RS performance with newer mac os builds by enabling SSSE3 with Clang in addition to GCC.
RS lib: make it work with older cmake versions.
Merge branch 'master' into topic/krb
RS lib: optimize "decode" internal loops, set optimization level to -O3 with release version. Add two and one block recovery to RS speed test/benchmark, report average "decode" / recovery throughput with speed benchmark.
Merge branch 'master' into topic/krb