clipboard: avoid clipboard during :global. #2809

This is equivalent to patches 7.4.396, 7.4.445 and 7.4.598.

vim-patch:7.4.396

Problem:    When 'clipboard' is "unnamed", :g/pat/d is very slow.
(Praful)
Solution:   Only set the clipboard after the last delete. (Christian
Brabandt)

1f285eb49a

vim-patch:7.4.445

Problem:    Clipboard may be cleared on startup.
Solution:   Set clip_did_set_selection to -1 during startup. (Christian
	    Brabandt)

1a19d37d90

vim-patch:7.4.598

Problem:    ":tabdo windo echo 'hi'" causes "* register not to be
changed.
	    (Salman Halim)
Solution:   Change how clip_did_set_selection is used and add
	    clipboard_needs_update and global_change_count.  (Christian
	    Brabandt)

af6a579263

Co-Author: @bfredl

src/nvim/ex_cmds2.c

@@ -41,6 +41,7 @@
 #include "nvim/memory.h"
 #include "nvim/move.h"
 #include "nvim/normal.h"
+#include "nvim/ops.h"
 #include "nvim/option.h"
 #include "nvim/os_unix.h"
 #include "nvim/path.h"
@@ -1838,6 +1839,8 @@ void ex_listdo(exarg_T *eap)
      * great speed improvement. */
     save_ei = au_event_disable(",Syntax");
 
+  start_global_changes();
+
   if (eap->cmdidx == CMD_windo
       || eap->cmdidx == CMD_tabdo
       || P_HID(curbuf)
@@ -1988,6 +1991,7 @@ void ex_listdo(exarg_T *eap)
     apply_autocmds(EVENT_SYNTAX, curbuf->b_p_syn,
         curbuf->b_fname, TRUE, curbuf);
   }
+  end_global_changes();
 }
 
 /*