Revert previous commit.

Revert previous commit.
(Note to self read the description first)

"Returns :

a newly-allocated string, with all the upper case characters in str converted to lower case, with semantics that exactly match g_ascii_tolower(). (Note that this is unlike the old g_strdown(), which modified the string in place.)"

git-svn-id: http://anonsvn.wireshark.org/wireshark/trunk@38395 f5534014-38df-0310-8fa8-9805f1628bb7