Details:
- Added two new sets of [sd]gemm micro-kernels for haswell architectures,
one that is 4x24/4x12 (s and d) and one that is 6x16/6x8.
- Changed the haswell configuration to use the 6x16/6x8 micro-kernels
by default.
- Updated various Makefiles, in test, test/3m4m, and testsuite.