The problem was an ab-use of last_rkey_length.
Formerly we saved the packed key length (of the search key)
in this element. But in certain cases it got replaced by
the (packed) result key length.
Now we use a new element of MI_INFO to save the packed key
length of the search key.
Added preliminary handling of symlinks in MyISAM.
When using myisamchk to check tables with --force, don't repair
tables that are marked as 'not closed' if they are ok.
Change fn_format() to use my_real_path and my_symlink
