Problem: SHOW CREATE TABLE printed garbage in table
  name for tables having TURKISH I
  (i.e. LATIN CAPITABLE LETTER I WITH DOT ABOVE)
  when lower-case-table-name=1.
  
  Reason: In some cases during lower/upper conversion in utf8,
  the result string can be shorter the original string
  (including the above letter). Old implementation of caseup_str()
  and casedn_str() didn't handle the result length properly,
  assuming that length cannot change.
  
  This fix changes the result type of cs->cset->casedn_str()
  and cs->cset->caseup_str() from VOID to UINT, to return
  the result length, as well as put '\0' terminator on a 
  proper place.
  
  Also, my_caseup_str_utf8() and my_casedn_str_utf8() were 
  rewritten not to use strlen() for performance purposes.
  It was done with help of adding of new functions - my_utf8_uni_no_range()
  and my_uni_utf8_no_range() - for null terminated strings.