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/screen.c b/src/screen.c
index 564eba3..306308b 100644
--- a/src/screen.c
+++ b/src/screen.c
@@ -2714,7 +2714,7 @@
      */
     if (VIsual_active && wp->w_buffer == curwin->w_buffer)
     {
-	if (ltoreq(curwin->w_cursor, VIsual))
+	if (LTOREQ_POS(curwin->w_cursor, VIsual))
 	{
 	    /* Visual is after curwin->w_cursor */
 	    top = &curwin->w_cursor;
@@ -3170,7 +3170,7 @@
     if (VIsual_active && wp->w_buffer == curwin->w_buffer)
     {
 					/* Visual is after curwin->w_cursor */
-	if (ltoreq(curwin->w_cursor, VIsual))
+	if (LTOREQ_POS(curwin->w_cursor, VIsual))
 	{
 	    top = &curwin->w_cursor;
 	    bot = &VIsual;