patch 8.1.0528: various typos in comments

Problem:    Various typos in comments.
Solution:   Fix the typos.
diff --git a/src/macros.h b/src/macros.h
index 1654e3e..e651d2b 100644
--- a/src/macros.h
+++ b/src/macros.h
@@ -192,7 +192,7 @@
 #   define mch_access(n, p)	access((n), (p))
 # endif
 # define mch_fstat(n, p)	fstat((n), (p))
-# ifdef MSWIN	/* has it's own mch_stat() function */
+# ifdef MSWIN	/* has its own mch_stat() function */
 #  define mch_stat(n, p)	vim_stat((n), (p))
 # else
 #  ifdef STAT_IGNORES_SLASH