Start the merging-rebase to v2.24.0-rc0

This commit starts the rebase of d44acf7 to 4359bc3

As it is the first chance to clean up during a rebase in quite a while,
this is a bit bigger. Mostly, commits and branches have been shuffled
around, the FSCache patches (while still not consolidated enough to
submit to the Git mailing list for review) are at least compile-clean
now, and the newest iteration of the `git add -i`/`git add -p` patches
were integrated.

Signed-off-by: Johannes Schindelin <[email protected]>

Author: dscho