patch 8.0.0714: when a timer causes a command line redraw " goes missing

Problem:    When a timer causes a command line redraw the " that is displayed
            for CTRL-R goes missing.
Solution:   Remember an extra character to display.

src/ex_getln.c

@@ -52,6 +52,8 @@ static int	cmd_showtail;		/* Only show path tail in lists ? */
 static int	new_cmdpos;	/* position set by set_cmdline_pos() */
 #endif
 
+static int	extra_char = NUL;  /* extra character to display when redrawing
+				    * the command line */
 #ifdef FEAT_CMDHIST
 typedef struct hist_entry
 {
@@ -1173,12 +1175,14 @@ getcmdline(
 		dont_scroll = TRUE;	/* disallow scrolling here */
 #endif
 		putcmdline('"', TRUE);
+		extra_char = '"';
 		++no_mapping;
 		i = c = plain_vgetc();	/* CTRL-R <char> */
 		if (i == Ctrl_O)
 		    i = Ctrl_R;		/* CTRL-R CTRL-O == CTRL-R CTRL-R */
 		if (i == Ctrl_R)
 		    c = plain_vgetc();	/* CTRL-R CTRL-R <char> */
+		extra_char = NUL;
 		--no_mapping;
 #ifdef FEAT_EVAL
 		/*
@@ -1755,8 +1759,10 @@ getcmdline(
 		ignore_drag_release = TRUE;
 #endif
 		putcmdline('^', TRUE);
+		extra_char = '^';
 		c = get_literal();	    /* get next (two) character(s) */
 		do_abbr = FALSE;	    /* don't do abbreviation now */
+		extra_char = NUL;
 #ifdef FEAT_MBYTE
 		/* may need to remove ^ when composing char was typed */
 		if (enc_utf8 && utf_iscomposing(c) && !cmd_silent)
@@ -1774,10 +1780,12 @@ getcmdline(
 		ignore_drag_release = TRUE;
 #endif
 		putcmdline('?', TRUE);
+		extra_char = '?';
 #ifdef USE_ON_FLY_SCROLL
 		dont_scroll = TRUE;	    /* disallow scrolling here */
 #endif
 		c = get_digraph(TRUE);
+		extra_char = NUL;
 		if (c != NUL)
 		    break;
 
@@ -3409,6 +3417,8 @@ redrawcmd(void)
     msg_no_more = FALSE;
 
     set_cmdspos_cursor();
+    if (extra_char != NUL)
+	putcmdline(extra_char, TRUE);
 
     /*
      * An emsg() before may have set msg_scroll. This is used in normal mode,