add intel/2014b toolchain definition, which includes GCC/4.8.3 as a dependency

depends on https://github.com/hpcugent/easybuild-easyblocks/pull/429 to ensure that FFTW wrappers libraries for Intel MKL are installed correctly

@gjbex, @hajgato, @jgtimmer: please review?
this is a conservative choice, maybe using the latest imkl v11.1.3.174 is also possible, I'm checking on that with Intel support