add eina_file_direct_ls()

add eina_file_direct_ls()

Similar to eina_file_ls(), but useful when one wants to apply some
filters to the names before using them as it provides sizes of the
whole path and basename, index of the basename inside the path, dirent
structure for reference (skip directories, etc) and last but not
least, it is faster as it does not stringshare or even builds the full
path at each iteration, instead it keeps the invariant prefix
untouched and just copy the filename.

All in all this is a faster version of eina_file_ls(), use it as
possible as it will avoid overheads.

git-svn-id: svn+ssh://svn.enlightenment.org/var/svn/e/trunk/eina@50065 7cbeb6ba-43b4-40fd-8cce-4c39aea84d33