CLEANUP: assorted typo fixes in the code and comments

This is 15th iteration of typo fixes
diff --git a/src/auth.c b/src/auth.c
index a3597d8..5d74f7a 100644
--- a/src/auth.c
+++ b/src/auth.c
@@ -49,7 +49,7 @@
 #endif
 
 /* find targets for selected groups. The function returns pointer to
- * the userlist struct ot NULL if name is NULL/empty or unresolvable.
+ * the userlist struct or NULL if name is NULL/empty or unresolvable.
  */
 
 struct userlist *