Use LAPACKE C bindings instead of Atlas specific bindings

[StefanBruens]

According to:
http://nicolas.limare.net/pro/notes/2014/10/31_cblas_clapack_lapacke/

LAPACKE is relatively recent (proposed in 2008, accepted in 2010) but it's the closest we have to a native C source-level interface to the original Fortran API. LAPACKE is to LAPACK what CBLAS is to BLAS, with this interface:
...
This one is standardized, as mentioned on Netlib: "Standard C language APIs for LAPACK".

Netlib Lapack is also available on significantly more distributions, compare Atlas:

and Lapack:

This also allows to use OpenBLAS or Intel MKL as Lapack/Blas implementation without any further work.

[StefanBruens]

While there is no dedicated autotool support for lapacke, it provides a standard pkgconfig file which can be used.