MDEV-30692: conf_to_src incompatible with CHARSET_INFO changes (postfix)

Caused by MDEV-30577 when the CHARSET_INFO structure changed.

As hinted by clang:

error: no member named 'csname' in 'struct charset_info_st'; did you mean 'cs_name'?

Because the target conf_to_src has the properties EXCLUDE_FROM_DEFAULT_BUILD
it hasn't been noticed.

Also correct:

 warning: field precision should have type 'int', but argument has type 'size_t'

Author: grooverdan

strings/conf_to_src.c

@@ -482,7 +482,7 @@ main(int argc, char **argv  __attribute__((unused)))
       if ( (!simple_cs_is_full(cs)) && (cs->cs_name.str))
       {
         snprintf(filename, sizeof filename, "%s/%.*s.xml",
-                 argv[1], cs->csname.length, cs->csname.str);
+                 argv[1], (int) cs->cs_name.length, cs->cs_name.str);
         my_read_charset_file(filename);
       }
       cs->state|= MY_CS_LOADED;