patch 8.2.2560: setting 'winminheigt' does not take tabline into account

Problem:    Setting 'winminheigt' does not take tabline into account.
Solution:   Subtract the tabline from the available height. (closes #7899)
diff --git a/src/window.c b/src/window.c
index 58a216d..a810a6a 100644
--- a/src/window.c
+++ b/src/window.c
@@ -5860,7 +5860,7 @@
     // loop until there is a 'winminheight' that is possible
     while (p_wmh > 0)
     {
-	room = Rows - p_ch;
+	room = Rows - p_ch - tabline_height();
 	needed = frame_minheight(topframe, NULL);
 	if (room >= needed)
 	    break;