vim-patch:7.4.312

Problem:    Cannot figure out what argument list is being used for a window.
Solution:   Add the arglistid() function. (Marcin Szamotulski)

https://code.google.com/p/vim/source/detail?r=v7-4-312
third-party: avoid using `rm` in the install command

Also, the command was removing only .so versions of the library, and not
the the `.dylib` under Mac OS X, and in a way that it would fail if the
files weren't present.

Instead, let's delegate to a CMake script--to get the portability--and
use a glob to detect and remove the shared versions of the library.
Hopefully, this will become unnecessary as msgpack's build becomes more
full-featured, and we can just tell it to build the static version
instead.
Merge pull request #1173 from jszakmeister/build-portability-fix

third-party: avoid using `rm` in the install command

closes #1171
Merge pull request #1169 from splinterofchaos/arglistid

vim-patch:7.4.312
eval.c: Rename has('neovim') feature to has('nvim')

To follow the convention of 'nvim' for technical references
runtime: Some nvim documentation fixes pointed by @oni-link