Add support for PRIMARY clipboard

runtime/plugin/nvim_gui_shim.vim

@@ -1,15 +1,15 @@
 " A Neovim plugin that implements GUI helper commands
 if !has('nvim') || exists('g:GuiLoaded')
-  finish
+	finish
 endif
 let g:GuiLoaded = 1
 
 if exists('g:GuiInternalClipboard')
 	function! provider#clipboard#Call(method, args) abort
 		if a:method == 'get'
-			return [rpcrequest(1, 'Gui', 'Clipboard', 'Get'), 'v']
+			return [rpcrequest(1, 'Gui', 'Clipboard', 'Get', a:args[0]), 'v']
 		elseif a:method == 'set'
-			call rpcnotify(1, 'Gui', 'Clipboard', 'Set', join(a:args[0], '
+			call rpcnotify(1, 'Gui', 'Clipboard', 'Set', a:args[2], join(a:args[0], '
 '))
 		endif
 	endfunction