Add support for passing options to the io layer using the URL syntax.  For 
example, /tmp/test.img?offset=1024.  Multiple options can separated using
the & character, although at the moment the only option implemented is
the offset option in the unix_io layer.

diff --git a/lib/ext2fs/ext2fs.h b/lib/ext2fs/ext2fs.h
index 19be9c5..6a02127 100644
--- a/lib/ext2fs/ext2fs.h
+++ b/lib/ext2fs/ext2fs.h
@@ -851,6 +851,10 @@
 extern errcode_t ext2fs_open(const char *name, int flags, int superblock,
 			     unsigned int block_size, io_manager manager,
 			     ext2_filsys *ret_fs);
+extern errcode_t ext2fs_open2(const char *name, const char *io_options, 
+			      int flags, int superblock, 
+			      unsigned int block_size, io_manager manager,
+			      ext2_filsys *ret_fs);
 extern blk_t ext2fs_descriptor_block_loc(ext2_filsys fs, blk_t group_block, 
 					 dgrp_t i);
 errcode_t ext2fs_get_data_io(ext2_filsys fs, io_channel *old_io);