[$] 5.18 Merge window, part 1

As of this writing, 4,127 non-merge changesets have found their way intothe mainline repository for the 5.18 development cycle. That may seem likea relatively slow start to the merge window, but there are a lot of changespacked into those commits. Read on for a summary of the mostsignificant changes to land in the first half of the 5.18 merge window.