Remove description of commit 1944cdc98, which has now been back-patched
so it's not relevant to v11 any longer. Add descriptions of other
recent commits that seemed worth mentioning.
I marked the update as stopping at 2018-07-30, because it's unclear
whether d06eebce5 will be allowed to stay in v11, and I didn't feel like
putting effort into writing a description of it yet. If it does stay,
I think it will deserve mention in the Source Code section.
87790fd1ea