or database name in logs

Problem was that InnoDB used filenam_to_tablename,
which do not handle partitions (due to the '#' in
the filename).

Solution is to add a new function for explaining
what the filename means: explain_filename.
It expands the database, table, partition and subpartition
parts and uses errmsg.txt for localization.
It also converts from my_charset_filename to system_charset_info
(i.e. human readable form for non ascii characters).
  http://lists.mysql.com/commits/70370

2773 Mattias Jonsson	2009-03-25

It has three different output styles.

NOTE: This is the server side ONLY part (introducing the explain_filename
function). There will be a patch for InnoDB using this function to solve
the bug.