Update cross compile info

Implement DYNAMIC_ARCH support for riscv64.  Three cpu types are
supported, riscv64_generic, riscv64_zvl256b, riscv64_zvl128b.
The two non-generic kernels require CPU support for RVV 1.0 to
function correctly.  Detecting that a riscv64 device supports
RVV 1.0 is a little complicated as there are some boards on the
market that advertise support for V via hwcap but only support
RVV 0.7.1, which is not binary compatible with RVV 1.0.  The
approach taken is to first try hwprobe.  If hwprobe is not
available, we fall back to hwcap + an additional check to distinguish
between RVV 1.0 and RVV 0.7.1.

Tested on a VM with VLEN=256, a CanMV K230 with VLEN=128 (with only
the big core enabled), a Lichee Pi with RVV 0.7.1 and a VF2 with no
vector.

A compiler with RVV 1.0 support must be used to build OpenBLAS for
riscv64 when DYNAMIC_ARCH=1.

Signed-off-by: Mark Ryan <markdryan@rivosinc.com>

Signed-off-by: Yuning Zhang <codeworm96@outlook.com>

There were some build options in the README that were not
highlighted. Now all are highlighted.

for #2723

prompted by #2388

Closes #2109

Found via `codespell -q 3 -w -L ith,als,dum,nd,amin,nto,wis,ba -S ./relapack,./kernel,./lapack-netlib`

Worth fixing, it gets in the way of searching....

The wording in some places is not grammatically correct. This change
also provides minor adjustments to the Markdown formatting which provide
modest improvements to readability.

Add POWER 8 to the list of additional architectures.

Optimized standard Blas Level-1,2 (excluding nrm2 functions) for z13 (double precision). Issue 884

IBM MASS library is upgraded to 8.1.5 and 8.1.3 is not available.
Update README.md and Makefile.power to use version 8.1.5 of libxlmass.