[easytag] Avoid C++ string conversion warnings

[David King <davidk src gnome org>]

commit 882f7ff40138fe7530c7ee5a46f8cf03a5c25705
Author: David King <amigadave amigadave com>
Date:   Thu Apr 10 17:14:10 2014 +0100

    Avoid C++ string conversion warnings
    
    Change the type of string literals to const gchar * in
    ET_File_Description.

 src/et_core.h |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/src/et_core.h b/src/et_core.h
index d5e67fe..10a1805 100644
--- a/src/et_core.h
+++ b/src/et_core.h
@@ -216,7 +216,7 @@ typedef struct _ET_File_Description ET_File_Description;
 struct _ET_File_Description
 {
     ET_File_Type FileType;    /* Type of file (ex: MP3) */
-    gchar       *Extension;   /* Extension (ex: ".mp3") */
+    const gchar *Extension; /* Extension (ex: ".mp3") */
     ET_Tag_Type  TagType;     /* Type of tag (ex: ID3) */
 };