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

test/functional/clipboard/clipboard_provider_spec.lua

@@ -285,6 +285,22 @@ describe('clipboard usage', function()
         the text]])
     end)
 
+    it('is updated on global changes', function()
+      insert([[
+	text
+	match
+	match
+	text
+      ]])
+      execute('g/match/d')
+      eq('match\n', eval('getreg("*")'))
+      feed('u')
+      eval('setreg("*", "---")')
+      execute('g/test/')
+      feed('<esc>')
+      eq('---', eval('getreg("*")'))
+    end)
+
   end)
 
   describe('with clipboard=unnamedplus', function()
@@ -329,6 +345,21 @@ describe('clipboard usage', function()
         really unnamed
         the plus]])
     end)
+    it('is updated on global changes', function()
+      insert([[
+	text
+	match
+	match
+	text
+      ]])
+      execute('g/match/d')
+      eq('match\n', eval('getreg("+")'))
+      feed('u')
+      eval('setreg("+", "---")')
+      execute('g/test/')
+      feed('<esc>')
+      eq('---', eval('getreg("+")'))
+    end)
   end)
 
   it('supports :put', function()