patch 8.1.1391: no popup window support

Problem:    No popup window support.
Solution:   Add initial code for popup windows.  Add the 'wincolor' option.
diff --git a/src/terminal.c b/src/terminal.c
index 1ceac3a..606a9db 100644
--- a/src/terminal.c
+++ b/src/terminal.c
@@ -3257,7 +3257,7 @@
 	else
 	    pos.col = 0;
 
-	screen_line(term->tl_toprow + pos.row, 0, pos.col, Columns, FALSE);
+	screen_line(term->tl_toprow + pos.row, 0, pos.col, Columns, 0);
     }
 
     term->tl_dirty_row_start = MAX_ROW;
@@ -3368,7 +3368,7 @@
 #ifdef FEAT_MENU
 				+ winbar_height(wp)
 #endif
-				, wp->w_wincol, pos.col, wp->w_width, FALSE);
+				, wp->w_wincol, pos.col, wp->w_width, 0);
     }
     term->tl_dirty_row_start = MAX_ROW;
     term->tl_dirty_row_end = 0;