EZC: fix bug in _zval_copy_ctor_func()

The type of the dest zval was copied from the source, but in the
KindOfStaticString case, the data of the dest zval is overwritten with a
plain string. This causes an assertion when the dest zval is used.

Enable the test which previously failed due to this bug.

Assuming I've done this right, this should be stacked on top of PR 1986.