Bug #2717: include/my_global.h mis-defines __attribute__

Fix when __attribute__() is stubbed out, add ATTRIBUTE_FORMAT() for specifying
  __attribute__((format(...))) safely, make more use of the format attribute,
  and fix some of the warnings that this turns up (plus a bonus unrelated one).


include/m_ctype.h:
  Add ATTRIBUTE_FORMAT to printf-like functions.
include/m_string.h:
  Add ATTRIBUTE_FORMAT to my_snprintf() declaration.
include/my_global.h:
  Fix neutering of __attribute__() on old versions of GCC and non-GCC compilers.
  Add ATTRIBUTE_FORMAT() macro for setting __attribute_((format(...)), since it
  is available from different versions of gcc and g++.
include/my_sys.h:
  Add ATTRIBUTE_FORMAT() to my_printf_error declaration
sql/item_subselect.cc:
  Silence warning about members being initialized out-of-order
sql/item_timefunc.cc:
  Fix format specifier in snprintf() calls with milliseconds
sql/mysql_priv.h:
  Add ATTRIBUTE_FORMAT to printf-like functions.
sql/mysqld.cc:
  Fix various format specifiers
  Make sure that method_conv is always set by myisam_stats_method
sql/opt_range.cc:
  Cast pointers to correct type for %lx
sql/set_var.cc:
  Fix __attribute__((unused)) (missing inner set of parens)
sql/slave.cc:
  Fix format specifier
sql/slave.h:
  Add ATTRIBUTE_FORMAT to slave_print_error() declaration.
sql/sql_acl.cc:
  Fix number of  arguments passed for formatting, and fix acl_host_or_ip being
  passed instead of just the hostname.
sql/sql_class.h:
  Add ATTRIBUTE_FORMAT to MYSQL_LOG::write().

include/m_string.h

@@ -247,7 +247,8 @@ extern ulonglong strtoull(const char *str, char **ptr, int base);
 
 extern int my_vsnprintf( char *str, size_t n,
                                 const char *format, va_list ap );
-extern int my_snprintf(char* to, size_t n, const char* fmt, ...);
+extern int my_snprintf(char *to, size_t n, const char *fmt, ...)
+  ATTRIBUTE_FORMAT(printf, 3, 4);
 
 #if defined(__cplusplus) && !defined(OS2)
 }