PHP 7 support broken in 1.2.3

[remicollet]

Because of e5da244

/dev/shm/BUILD/php74-php-pecl-krb5-1.2.3-build/php74-php-pecl-krb5-1.2.3/krb5-1.2.3/negotiate_auth.c:243:17: error: implicit declaration of function 'ZVAL_OBJ_COPY'; did you mean 'ZVAL_STR_COPY'? [-Wimplicit-function-declaration]
  243 |                 ZVAL_OBJ_COPY(&object->chan_bindings, Z_OBJ_P(zchannel));
      |                 ^~~~~~~~~~~~~
      |                 ZVAL_STR_COPY

Problem: package.xml states PHP >= 7.0

As version 1.2.3 is a bugfix version, will be better to keep PHP 7.x compatibility
(and remove it later, ex in 1.3.0)