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/version.c b/src/version.c
index caf1b64..7e4d0fe 100644
--- a/src/version.c
+++ b/src/version.c
@@ -765,6 +765,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    448,
+/**/
     447,
 /**/
     446,
@@ -2091,7 +2093,7 @@
     void
 maybe_intro_message(void)
 {
-    if (bufempty()
+    if (BUFEMPTY()
 	    && curbuf->b_fname == NULL
 #ifdef FEAT_WINDOWS
 	    && firstwin->w_next == NULL