patch 8.2.3465: cannot detect insert scroll mode

Problem:    Cannot detect insert scroll mode.
Solution:   Add "scroll" to complete_info(). (closes #8943)

runtime/doc/eval.txt

@@ -3883,6 +3883,8 @@ complete_info([{what}])				*complete_info()*
 		   ""		     Not in completion mode
 		   "keyword"	     Keyword completion |i_CTRL-X_CTRL-N|
 		   "ctrl_x"	     Just pressed CTRL-X |i_CTRL-X|
+		   "scroll"	     Scrolling with |i_CTRL-X_CTRL-E| or
+				     |i_CTRL-X_CTRL-Y|
 		   "whole_line"	     Whole lines |i_CTRL-X_CTRL-L|
 		   "files"	     File names |i_CTRL-X_CTRL-F|
 		   "tags"	     Tags |i_CTRL-X_CTRL-]|

src/insexpand.c

@@ -68,7 +68,7 @@ static char *ctrl_x_msgs[] =
 static char *ctrl_x_mode_names[] = {
 	"keyword",
 	"ctrl_x",
-	"unknown",	    // CTRL_X_SCROLL
+	"scroll",
 	"whole_line",
 	"files",
 	"tags",
@@ -2539,7 +2539,8 @@ f_complete_check(typval_T *argvars UNUSED, typval_T *rettv)
     static char_u *
 ins_compl_mode(void)
 {
-    if (ctrl_x_mode == CTRL_X_NOT_DEFINED_YET || compl_started)
+    if (ctrl_x_mode == CTRL_X_NOT_DEFINED_YET || ctrl_x_mode == CTRL_X_SCROLL
+	    || compl_started)
 	return (char_u *)ctrl_x_mode_names[ctrl_x_mode & ~CTRL_X_WANT_IDENT];
 
     return (char_u *)"";

src/testdir/test_popup.vim

@@ -990,6 +990,10 @@ func Test_popup_complete_info_01()
         \ ["\<C-X>", 'ctrl_x'],
         \ ["\<C-X>\<C-N>", 'keyword'],
         \ ["\<C-X>\<C-P>", 'keyword'],
+        \ ["\<C-X>\<C-E>", 'scroll'],
+        \ ["\<C-X>\<C-Y>", 'scroll'],
+        \ ["\<C-X>\<C-E>\<C-E>\<C-Y>", 'scroll'],
+        \ ["\<C-X>\<C-Y>\<C-E>\<C-Y>", 'scroll'],
         \ ["\<C-X>\<C-L>", 'whole_line'],
         \ ["\<C-X>\<C-F>", 'files'],
         \ ["\<C-X>\<C-]>", 'tags'],

src/version.c

@@ -757,6 +757,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    3465,
 /**/
     3464,
 /**/