Start the merging-rebase to junio/maint

This commit starts the rebase of 62f3116 to 23415c2

This is just an intermediate rebase, used as an excuse for a little bit
of cleanup:

- a patch was moved from win-test-fixes to remote-hg-prerequisites,
  where it really belongs

- the interactive-rebase branch thicket and the status-v2-porcelain
  patch series have been updated to their newest respective iterations.

- rebased jeffhostetler/vs2015 to make it easier to upstream the
  patches.

- the "use OpenSSL's SHA-1 routines for a nice speedup" patch got an
  updated commit message and was moved to the msys2 patches.

- the cat-file-filters branch was updated to its latest iteration.

- the mingw/default-ident patch series was moved closer to the front, so
  that it can be upstreamed before the more complicated patch series.

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

Author: dscho