cmake: upgrade libuv 0.11.23 -> 0.11.26 #911

Fixes some bugs and increase the performance of uv_hrtime() on OSX, which
reduces its prominence in performance traces. This allows us to better see
what's really causing slowness.

ref:
- https://github.com/neovim/neovim/issues/868
- https://github.com/joyent/libuv/pull/1325
- https://github.com/joyent/libuv/releases
Add vim_feedkeys API function

- New API function to push data to the typeahead buffer - this should
  equivalent to the vimscript feedkeys() function
- In Vim there was a --remote-send command to insert input into a
  Vim server instance. Besides accepting key sequences it also
  translated special keys such as <CR> or <Leader>, backslash notation
  is ignored. This commit backports the original Vim handler for
  --remote-send as a bool option for vim_feedkeys()
- vim-patch:0
dispatch function generator: Fix bug in validation/initialization

- Initialize variables before validating argument count to remove possibility of
  freeing uninitialized pointers
- Set the error when the argument count validation fails
Merge pull request #916 'Add `feedkeys` API function'