formatting README.md

Update version string & release date.

update version string to 8.2.1

Add target_compile_features() for superlu_dist target.

updates to prepare for v8.1.2 release.

Prepare v8.1.1 release: update version number, doxygen files

upadte version string

FIX: in sp_ienv.c, enforce RELAX to be bounded by MAXSUP.

changed installation dirs of example drivers to /EXAMPLE

Bug fix: in "dReDistributre_A", dereference several uninitialized/una…

…llocated arrays even though their sizes are zero.

Upgrade to v7.1.1