Update runtime files.

https://github.com/vim/vim/commit/cd5c8f82507822467232ab71e1ebbaae19595916

Problem:    The justify plugin has to be copied or sourced to be used.
Solution:   Turn it into a package.

https://github.com/vim/vim/commit/2946d0236dc9e23ec0050feacdb959b9ae5672a8

Justification for changes that do not carry over

- `Filelist` does not exist in neovim
- neovim does not have a `README.txt` in `runtime/macros`

Problem:    The shellmenu plugin has to be copied or sourced to be used.
Solution:   Turn it into a package.

https://github.com/vim/vim/commit/fead3ac9a35e0fc358141d3eb19574cd8a3ecb55

Justification for changes that do not carry over

- `Filelist` does not exist in neovim
- neovim does not have a `README.txt` in `runtime/macros`

Problem:    The swapmous plugin has to be copied or sourced to be used.
Solution:   Turn it into the swapmouse package.

https://github.com/vim/vim/commit/e101204906e10f1e100e2f9017985c61f26b03ac

Justification for changes that do not carry over

- `Filelist` does not exist in neovim
- neovim does not have a `README.txt` in `runtime/macros`

Update runtime files.

https://github.com/vim/vim/commit/e392eb41f8dfc01bd13634e534ac6b4d505326f4

Files runtime/doc/tags and runtime/doc/todo.txt did not exist. Ignored
runtime/syntax/vim.vim. One change in runtime/doc/windows.txt had already been
applied.

This macro does the same thing as `set keymap=dvorak`, so it serves no
purpose.

Update runtime files.

https://code.google.com/p/vim/source/detail?r=5d89d9b40499059e1a64dc35fbae94313fba0098

Re: compatibility issues with users doing `:so
$VIMRUNTIME/macros/matchit.vim`

Fixes #2918