Another bug from the tracker, reported by Mike Stramba.
A duplicated Py_XDECREF in the wrong place made assigning
arrays from Vector objects not work.
Also, fixed nasty bug in C API of idproperties (the function
to look up a property from a group was broken). Fixed a memory
leak too.
In addition, made "del group['property']" delete properties
from group; previously this would just crash (or at least it
should have). Added a small addition to the example in the
epydocs for IDGroup.
71da111613