[php] Actually implement abstract_inherit_runme.php

The previous version didn't really test anything useful.  Now we
check that trying to instantiate any of the abstract classes fails
with the expected error.

TODO

@@ -204,10 +204,6 @@ PHP
        mapping to the same object in case it gets twice destroyed.  And check
        if ref count destroying is even working, see smart_pointer_rename
 
-*      Work out how classes without even inherited constructors should
-       interact with the php "new <class>" notation.
-       See: abstract_inherit_wrap.cpptest
-
 **     Look at pass by point and passby ref,
        Make sometype** to be auto allocated
        Make sometype& and sometype* to be autoallocated IF THEY ARE NOT