vim-patch:8.0.0448: some macros are lower case (#7936)

Problem:    Some macros are in lower case, which can be confusing.
Solution:   Make a few lower case macros upper case.
b5aedf3e22

ref #6297

src/nvim/spell.c

@@ -7147,7 +7147,7 @@ void ex_spelldump(exarg_T *eap)
   set_option_value("spl",  dummy, (char *)spl, OPT_LOCAL);
   xfree(spl);
 
-  if (!bufempty()) {
+  if (!BUFEMPTY()) {
     return;
   }