add option "USE_ORIGINAL_LAPACK" to prefer found ${LAPACK_LIBRARIES}
over the ones found in ${ATLAS_LIBRARIES} during linker-stage, because
some versions of liblapack.so provided by ATLAS are missing some needed
symbols from the original LAPACK library -- this is case on el5, e.g.
Merge pull request #1608 from besser82/fix_lapack_cmake

add option "USE_ORIGINAL_LAPACK"