Initialize an array to quiet compiler complaining.

Some versions of GCC think this can be used uninitialized. It doesn't appear
 to be the case, but we initialize it to keep the compiler happy. It's probably
 a good idea anyhow.

archivers/zip.c

@@ -375,7 +375,7 @@ static int ZIP_fileClose(fvoid *opaque)
 static PHYSFS_sint64 zip_find_end_of_central_dir(void *in, PHYSFS_sint64 *len)
 {
     PHYSFS_uint8 buf[256];
-    PHYSFS_uint8 extra[4];
+    PHYSFS_uint8 extra[4] = { 0, 0, 0, 0 };
     PHYSFS_sint32 i = 0;
     PHYSFS_sint64 filelen;
     PHYSFS_sint64 filepos;