CLEANUP: assorted typo fixes in the code and comments

This is 27th iteration of typo fixes
diff --git a/src/hlua.c b/src/hlua.c
index 1dbaaa3..758341a 100644
--- a/src/hlua.c
+++ b/src/hlua.c
@@ -6077,7 +6077,7 @@
 	return hlua_http_rep_hdr(L, msg, 1);
 }
 
-/* Matches all comma-separated values of all occurences of an header in the HTTP
+/* Matches all comma-separated values of all occurrences of an header in the HTTP
  * message given its name against a regex and replaces it if it matches. It
  * relies on hlua_http_rep_hdr().
  */