Problem was that there are no support for symlinked files on Windows for
mysqld. So we fail when trying to create them.

Solution: Ignore the DATA/INDEX DIRECTORY clause for partitions and push
a warning. (Just like a MyISAM table)

- The function build_table_filename() builds up a string unconditionally 
using the forward slash as a path separator. Later, when the string is 
searched for FN_LIBCHAR by the set_up_table_before_create() function, a 
null pointer is returned that is finally used by strlen in the 
append_file_to_dir() function which causes the crash.