Fixed segfault when a sub-class tried to redefine a property accessor as
a standard property with no accessors.  In this case the sub-class
inherits the accessors even though they are not defined by the
sub-class.
Implementing classes can now satisfy guarded property declarations with
a traditional property declaration.

Also added XFAIL sections to a few tests that are expected to fail for
now until other tickets are closed.

fixes #13
Added two interface tests.
Use $foo->get style name for accessor methods