Update textobj-user to 0.3.12.

Make it a bundle while we're at it.
Set iskeyword while editing help files.

It got frustrating that it wasn't easy to test links to other
documentation because iskeyword was not set the same way as when you are
viewing help files via :help.  This sets iskeyword so that it matches
how it's set while viewing help so that jumping to links like
'textobj-indent.txt' work correctly.
Add textobj-function.
Update textobj-indent.
Update lusty-explorer and lusty-juggler.
Use &previewwindow to detect a Fugitive :Gstatus window.

This is a better work-around than checking the number
of windows.
Automatically close diff window after a Git commit.
Merge branch 'js/mine'
Merge branch 'js/textobj-updates'
Merge branch 'js/fix-edit-help-keywords'
Add "@" to help file 'iskeyword' for accented alphabetic characters.
Merge branch 'js/update-lusty'
Remove obsolete SQUASH_MSG file handling.
Use full :setfiletype keyword.
Cleanup auto-commands for filetypes and last cursor position.
Sync with upstream.