Bug#45012 my_like_range_cp932 generates invalid string

Problem: The functions my_like_range_xxx() returned
badly formed maximum strings for Asian character sets,
which made problems for storage engines.

Fix: 
- Removed a number my_like_range_xxx() implementations,
  which were in fact dumplicate code pieces.
- Using generic my_like_range_mb() instead.
- Setting max_sort_char member properly for Asian character sets
- Adding unittest/strings/strings-t.c, 
  to test that my_like_range_xxx() return well-formed 
  min and max strings.

Notes:

- No additional tests in mysql/t/ available.
  Old tests cover the affected code well enough.

unittest/strings/strings-t.c

@@ -0,0 +1,114 @@
+/* Copyright 2000, 2010, Oracle and/or its affiliates. All rights reserved.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; version 2 of the License.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA */
+
+#include <tap.h>
+#include <my_global.h>
+#include <my_sys.h>
+
+
+/*
+  Test that like_range() returns well-formed results.
+*/
+static int
+test_like_range_for_charset(CHARSET_INFO *cs, const char *src, size_t src_len)
+{
+  char min_str[32], max_str[32];
+  size_t min_len, max_len, min_well_formed_len, max_well_formed_len;
+  int error= 0;
+  
+  cs->coll->like_range(cs, src, src_len, '\\', '_', '%',
+                       sizeof(min_str),  min_str, max_str, &min_len, &max_len);
+  diag("min_len=%d\tmax_len=%d\t%s", min_len, max_len, cs->name);
+  min_well_formed_len= cs->cset->well_formed_len(cs,
+                                                 min_str, min_str + min_len,
+                                                 10000, &error);
+  max_well_formed_len= cs->cset->well_formed_len(cs,
+                                                 max_str, max_str + max_len,
+                                                 10000, &error);
+  if (min_len != min_well_formed_len)
+    diag("Bad min_str: min_well_formed_len=%d min_str[%d]=0x%02X",
+          min_well_formed_len, min_well_formed_len,
+          (uchar) min_str[min_well_formed_len]);
+  if (max_len != max_well_formed_len)
+    diag("Bad max_str: max_well_formed_len=%d max_str[%d]=0x%02X",
+          max_well_formed_len, max_well_formed_len,
+          (uchar) max_str[max_well_formed_len]);
+  return
+    min_len == min_well_formed_len &&
+    max_len == max_well_formed_len ? 0 : 1;
+}
+
+
+static CHARSET_INFO *charset_list[]=
+{
+#ifdef HAVE_CHARSET_big5
+  &my_charset_big5_chinese_ci,
+  &my_charset_big5_bin,
+#endif
+#ifdef HAVE_CHARSET_euckr
+  &my_charset_euckr_korean_ci,
+  &my_charset_euckr_bin,
+#endif
+#ifdef HAVE_CHARSET_gb2312
+  &my_charset_gb2312_chinese_ci,
+  &my_charset_gb2312_bin,
+#endif
+#ifdef HAVE_CHARSET_gbk
+  &my_charset_gbk_chinese_ci,
+  &my_charset_gbk_bin,
+#endif
+#ifdef HAVE_CHARSET_latin1
+  &my_charset_latin1,
+  &my_charset_latin1_bin,
+#endif
+#ifdef HAVE_CHARSET_sjis
+  &my_charset_sjis_japanese_ci,
+  &my_charset_sjis_bin,
+#endif
+#ifdef HAVE_CHARSET_tis620
+  &my_charset_tis620_thai_ci,
+  &my_charset_tis620_bin,
+#endif
+#ifdef HAVE_CHARSET_ujis
+  &my_charset_ujis_japanese_ci,
+  &my_charset_ujis_bin,
+#endif
+#ifdef HAVE_CHARSET_utf8
+  &my_charset_utf8_general_ci,
+  &my_charset_utf8_unicode_ci,
+  &my_charset_utf8_bin,
+#endif
+};
+
+
+int main()
+{
+  size_t i, failed= 0;
+  
+  plan(1);
+  diag("Testing my_like_range_xxx() functions");
+  
+  for (i= 0; i < array_elements(charset_list); i++)
+  {
+    CHARSET_INFO *cs= charset_list[i];
+    if (test_like_range_for_charset(cs, "abc%", 4))
+    {
+      ++failed;
+      diag("Failed for %s", cs->name);
+    }
+  }
+  ok(failed == 0, "Testing my_like_range_xxx() functions");
+  return exit_status();
+}