* added patch for intel-tbb@2019.1: with old compilers
* sparately specify when @:2018 and @2019
the reason we can't say @:2019 is that would include @2019.1 where the
patch doesn't work.
* should be possible to list when constraint as @:2019
According to my reading of ["Version ranges" in the Spack
docs](https://spack.readthedocs.io/en/latest/packaging_guide.html#version-ranges),
this should apply to up to `2019` but not `2019.1:`
* @:2019.0 appears to be necessary to specify 2019 but not 2019.1
* specifying 2019.1 2019.2 2019.3 2019.4 separately and explcitly
* flake8 fixes for long lines.
* add comments to explain why so many different patch directives
* remove blank like for flake8
* revert spec %gcc@4.8.0:4.99999 -> %gcc@4.8.0:
92604ed576