Details:
- Defined a new function, bli_string_mkupper(), that calls toupper() on
every non-NULL character in a string.
- Call bli_string_mkupper() prior to calling xerbla_() in the level-2/-3
BLAS _check() macros. This prevents the BLAS testsuite from complaining
that the operation name (e.g. "dgemm") does not match the expected
value (e.g. "DGEMM"). Thanks to Dave Love for reporting this issue.
