Fix Makefiles to support OpenMP on AIX for xlc (clang) with xlf.

* Fixed gemmt, imatcopy, zimatcopy_cnc functions
* Fixed cblas_cscal testing in ctest
* Removed rotmg unreacheble code
* Added zero size checks

There are two instances when building the tests where OpenBLAS fails to
build with OpenMP and clang due to library paths getting reset as flags
are set rather than appended. This seems to only affect certain
clang/libomp installations, but if it's already grabbing the correct
library paths we might as well use them.

* Add C conversions of the CBLAS tests for NOFORTRAN=1 builds

* Enable CTEST without Fortran and fix passing of BUILD_vartype options to exports/gensymbol

add misc fixes.

make sure that test cases cover all code path when kernel uses looping unrolling.

make sure that test cases cover all code path when kernel uses looping unrolling.

The main Makefile takes care of this in the build process, but users or CI jobs may try to run this directly

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

Various fixes for const correctness, stray tab characters and unused labels

If OpenBLAS is built using add_subdirectory(OpenBlas) as part of another project
then the paths set by CMAKE_XXX_DIR are relative to the parent project
and not the OpenBLAS project.

The NTRA argument can be equal to -1 if one does not want a snapshot file
(and this is the case with sample data {s,d,c,z}in3).
The routines {S,D,C,Z}PRCN3 will try to use their first argument as an output
unit number, so we avoid calling them when NTRA < 0.

Patch originally written by Camm Maguire.

The SNAME variable contains names of C functions like "cblas_dgemv".
Apparently the code was not taking into account the 6-letter "cblas_"
prefix when determining the task to be done.

The issue does not affect c_{s,d,c}blat2.f, which use the correct
offsetting.

Patch originally written by Camm Maguire.