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, @JensTimmerman: please review?
reply from Intel support:

```
Intel compilers v13.1.x are officially supported by MKL 11.1.x. So yes, it is safe to use the latest MKL release with icc/ifort 2013.5.192. 

However, when MKL 11.2 comes out later this year (Q4) and if you decide to use it then we'd strongly recommend you to update your compilers to v14.x. This is mainly because of OpenMP compatibility requirement. MKL 11.2 may have issues with OpenMP runtimes provided by compilers earlier than v14.
```

So, I'll update this PR to use the latest imkl version.