patch 8.0.0448: some macros are in lower case

Problem:    Some macros are in lower case, which can be confusing.
Solution:   Make a few lower case macros upper case.
diff --git a/src/ui.c b/src/ui.c
index 4da79f0..d89c500 100644
--- a/src/ui.c
+++ b/src/ui.c
@@ -442,7 +442,7 @@
     /* If visual mode is only due to a redo command ("."), then ignore it */
     if (!redo_VIsual_busy && VIsual_active && (State & NORMAL))
     {
-	if (lt(VIsual, curwin->w_cursor))
+	if (LT_POS(VIsual, curwin->w_cursor))
 	{
 	    start = VIsual;
 	    end = curwin->w_cursor;
@@ -456,8 +456,8 @@
 	    start = curwin->w_cursor;
 	    end = VIsual;
 	}
-	if (!equalpos(clip->start, start)
-		|| !equalpos(clip->end, end)
+	if (!EQUAL_POS(clip->start, start)
+		|| !EQUAL_POS(clip->end, end)
 		|| clip->vmode != VIsual_mode)
 	{
 	    clip_clear_selection(clip);