Updated common log interface.

[LarsAsplund]

Update common log interface as outlined in OSVVM/OSVVM#80

[umarcor]

@LarsAsplund please add a fragment to https://github.com/VUnit/vunit/tree/master/docs/news.d corresponding to this PR.

[LarsAsplund]

@umarcor Actually, it was already added with reference to #776. See https://github.com/VUnit/vunit/blob/master/docs/news.d/776.feature.rst

[umarcor]

@LarsAsplund in those cases, just copy and paste the file with a different number in the filename but exactly the same content. See, for instance, e24d818 and http://vunit.github.io/release_notes.html#features.

I would like to contribute an enhancement to towncrier in order to handle these cases better. Yet, for now, this is the solution.

[LarsAsplund]

@umarcor Will do.

[LarsAsplund]

@umarcor Hm, my latest push with common log updates came with its own branch/PR. Should that have generated yet another news item?

[umarcor]

@LarsAsplund yes. in the end, we want all the issues/PRs related to this change/item/feature to show as a single list in http://vunit.github.io/release_notes.html#features.
However, if you are going to push a docs/news.d: cp 776 949 or docs/news.d: cp 947 949 only, do push that to master straightaway.