Merge branch 'PHP-5.6' into PHP-7.0

* PHP-5.6:
  Use STR_EMPTY_ALLOC macro instead
  Fix DateInterval::format segfault

diff --cc ext/date/php_date.c
index c2ef1778945fba035c00e70caa68d0fa1b29e779,750800da4c8e3ee234c8c11309977fcaedab77ed..e780b2ee6b723234cb7e00554d43f03b0f2ff875
--- 1/ext/date/php_date.c
--- 2/ext/date/php_date.c
+++ b/ext/date/php_date.c
@@@ -4270,7 -4359,11 +4270,11 @@@ static zend_string *date_interval_forma
  
        smart_str_0(&string);
  
 -      if (string.c == NULL) {
 -              return STR_EMPTY_ALLOC();
++      if (string.s == NULL) {
++              return ZSTR_EMPTY_ALLOC();
+       }
+ 
 -      return string.c;
 +      return string.s;
  }
  /* }}} */