WL#1324 table name to file name encoding

- Encoding itself, implemented as a charset
  "filename". Originally planned to use '.'
  as an escape character, but now changed to '@'
  for two reasons: "ls" does not return
  file names starting with '.' considering them
  as a kind of hidden files; some platforms
  do not allow several dots in a file name.
- replacing many calls of my_snprintf() and
  strnxmov() to the new build_table_filename().
- Adding MY_APPEND_EXT mysys flag, to append
  an extention rather that replace it.
- Replacing all numeric constants in fn_format
  flag arguments to their mysys definitions, e.g.
  MY_UNPACK_FILENAME,
- Predictability in several function/methods:
  when a table name can appear with or withot .frm
  extension. Some functions/methods were changed
  so accept names strictly with .frm, other - strictly
  without .frm extensions. Several DBUG_ASSERTs were
  added to check whether an extension is passed.
Many files:
  table name to file name encoding
mysql_priv.h:
  Prototypes for new table name encoding tools.
ctype-utf8.c:
  Implementing "filename" charset for
  table name to file name encoding.
row0mysql.c:
  Fixing table name prefix.
mf_format.c:
  Adding MY_APPEND_EXT processing.
Many files:
  Fixing tests.
my_sys.h:
  Adding new flag to append rather than replace an extension.
m_ctype.h:
  Adding "filename" charset definition.

sql/sql_rename.cc

@@ -155,18 +155,15 @@ rename_tables(THD *thd, TABLE_LIST *table_list, bool skip_error)
       old_alias= ren_table->table_name;
       new_alias= new_table->table_name;
     }
-    sprintf(name,"%s/%s/%s%s",mysql_data_home,
-	    new_table->db, new_alias, reg_ext);
-    unpack_filename(name, name);
+    build_table_filename(name, sizeof(name),
+                         new_table->db, new_alias, reg_ext);
     if (!access(name,F_OK))
     {
       my_error(ER_TABLE_EXISTS_ERROR, MYF(0), new_alias);
       DBUG_RETURN(ren_table);			// This can't be skipped
     }
-    sprintf(name,"%s/%s/%s%s",mysql_data_home,
-	    ren_table->db, old_alias,
-	    reg_ext);
-    unpack_filename(name, name);
+    build_table_filename(name, sizeof(name),
+                         ren_table->db, old_alias, reg_ext);
 
     frm_type= mysql_frm_type(thd, name, &table_type);
     switch (frm_type)