Blocked gemm with a *bad* pack method.  So students will see a negative impact on performance related to cache sizes.
Juste removed the C99 crap (restrict keyword).  We still have the *bad* pack
simple variant of packing following the elements with stride 1
We are achieving 96% performance of OpenBLAS!
Ugly but fasr
Cleanup:  Micro kernel can be selected by defining macros.  See src/Makefile