dependencies: Update to libuv 0.11.28
Merge PR #1047 'Update libuv to 0.11.28'
Add helper cstr_as_string()

- Add nocopy helper alternative to cstr_to_string
Refactor vim_feedkeys and f_feedkeys

- To clean up the mix between feedkeys and replace_termcodes
  the vim_feedkeys API function now does the same thing as the
  vimscript feedkeys() function
- The original f_feedkeys() function now calls the vim_feedkeys()
  function from the API
Add API vim_replace_termcodes

- Add API function to call replace_termcodes
Merge pull request #920 'Add `feedkeys` API function part 2'
api: Implement the 'redraw:tabs' event
api: Implement the 'redraw:insert_line' event
api: Implement the 'redraw:delete_line' event
syntax: Store RGB color information in cterm attribute entries.

This is a temporary hack: When terminal dependencies are removed, only RGB will
be used to describe colors(terminal-specific UIs will translate RGB to terminal
color codes)
api: Implement the 'redraw:update_line' event
api: Implement the 'redraw:status_line' event
api: Implement the 'redraw:ruler' event
api: Implement the 'redraw_{fore,back}ground_color' events
api: Implement the 'redraw:layout' event
api: Implement the 'redraw:cursor' event
api: Implement the 'redraw:win_end' event
api: Implement vim_request_screen to force redraw events
api: Implement vim_command_output function

This function can be used by API clients to execute a command and capture the
output.
Use character offsets instead of byte offsets for attributes