Replace PHP_TM_GMTOFF with AC_CHECK_MEMBERS

Changes:
- PHP_TM_GMTOFF removed
- HAVE_TM_GMTOFF replaced with HAVE_STRUCT_TM_TM_GMTOFF
- HAVE_TM_ZONE replaced with HAVE_STRUCT_TM_TM_ZONE
- HAVE_TZNAME removed

The PHP_TM_GMTOFF macro can be replaced with Autoconf's AC_CHECK_MEMBERS
that defines the HAVE_STRUCT_TM_TM_GMTOFF symbol instead of the
HAVE_TM_ZONE.

The HAVE_TZNAME symbol is not used in current code. The obsolete
HAVE_TM_ZONE symbol has been replaced with more proper
HAVE_STRUCT_TM_TM_ZONE. These are defined by the AC_STRUCT_TIMEZONE
macro.

Author: petk

ibase_query.c

@@ -1390,7 +1390,7 @@ static int _php_ibase_var_zval(zval *val, void *data, int type, int len, /* {{{
 			   always sets tm_isdst to 0, sometimes incorrectly (InterBase 6 bug?)
 			*/
 			t.tm_isdst = -1;
-#if HAVE_TM_ZONE
+#if HAVE_STRUCT_TM_TM_ZONE
 			t.tm_zone = tzname[0];
 #endif
 			if (flag & PHP_IBASE_UNIXTIME) {