configure BUGFIX: GSL may be linked against cblas_... functions or just ..., this is fixed.
Before we checked for cblas_dnrm2. However, e.g. libgoto names it simply dnrm2. Hence, the blas functions are not found or slower (c)blas, or gsl(c)blas is used. Now, we simply check for dnrm2 functions in the list of libs first, if it fails, then for cblas_dnrm2. And finally, we test GSL functionality by checking for main(), which only works if a working blas lib has been found before.
Also, we removed AC_MSG_NOTICE about CFLAGS and others. However, the other for MPICC was left present.
