mke2fs: configure encoding during superblock initialization

mke2fs: configure encoding during superblock initialization

This patch implements two new extended options to mkefs, allowing the
user to specify an encoding for file name operations and encoding flags
during filesystem creation.  We provide default flags for each encoding,
which the user can overwrite by passing -E fname_encoding-flags to mkfs.

If the user doesn't specify an encoding, the default value from
options.fname_encoding in mke2fs.conf.in file will be used.

Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>