patch 9.0.0828: various typos

Problem:    Various typos.
Solution:   Correct typos. (closes #11432)
diff --git a/src/config.h.in b/src/config.h.in
index ef0637a..b77418c 100644
--- a/src/config.h.in
+++ b/src/config.h.in
@@ -135,7 +135,7 @@
 /* Define if struct sigcontext is present */
 #undef HAVE_SIGCONTEXT
 
-/* Define if touuper/tolower only work on lower/upercase characters */
+/* Define if toupper/tolower only work on lower/uppercase characters */
 #undef BROKEN_TOUPPER
 
 /* Define if stat() ignores a trailing slash */