blas-f77 compatibility check

[John W. Eaton]

On  2-Apr-2008, Jaroslav Hajek wrote:

| Er, no, I don't think so. HAVE_BLAS will be false, and BLAS_LIBS
| empty, and BLAS_DIR="blas". In such case, the reference BLAS in
| libcruft will be used (compiled by the current Fortran compiler), so I
| see no problems. The incompatible BLAS library will not be used at
| all.

OK, I misunderstood the message.

jwe