Allocate memory when a character set is requested:

- For simple character sets: from_uni convertion table.
- For UCA: alternative weight arrays.
Use mbminlen instead of MY_CS_NONTEXT

strings/ctype-czech.c

@@ -572,6 +572,7 @@ static MY_UNI_IDX idx_uni_8859_2[]={
 
 static MY_COLLATION_HANDLER my_collation_latin2_czech_ci_handler =
 {
+  NULL,			/* init */
   my_strnncoll_czech,
   my_strnncollsp_czech,
   my_strnxfrm_czech,