Convert between journal features and strings

[Girish Shilamkar <Girish.Shilamkar@Sun.COM>]

Hi Ted,
	e2p_string2feature() and e2p_feature2string() can operate on ext2/3/4
features list as there is only one struct feature feature_list[] and no
corresponding journal features list. 
After introducing journal_checksum and journal_async_commit features, we
needed to display the features using debugfs which does it through the
two e2p_* functions. A new struct feature jrnl_feature_list[] was added.
The e2p_* functions were passed an additional argument so it can decide
which feature list to use.
Change in the APIs of e2p_* functions might not be acceptable so we have
an option to either make e2p_feature2string2() function or add
a new e2p_jnl_feature2string()

Would like to know what will be preferred e2p_feature2string2() or
e2p_jnl_feature2string() ?

Thanks,
Girish