Compare a filename ignoring letter case on OS/2

Signed-off-by: Rafaël Carré <funman@videolan.org>
(cherry picked from commit 066c6231)
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

modules/demux/mkv/mkv.cpp

@@ -173,7 +173,7 @@ static int Open( vlc_object_t * p_this )
                     {
                         s_filename = s_path + DIR_SEP_CHAR + psz_file;
 
-#ifdef WIN32
+#if defined(WIN32) || defined(__OS2__)
                         if (!strcasecmp(s_filename.c_str(), p_demux->psz_file))
 #else
                         if (!s_filename.compare(p_demux->psz_file))