Fix volatile vs. pointer confusion

Variables used after a longjmp() need to be declared volatile.  In
case of a pointer, it's the pointer itself that needs to be declared
volatile, not the pointed-to value.  So we need

    PyObject *volatile items;

instead of

    volatile PyObject *items;  /* wrong */

Attached patch fixes a couple of cases of that.  Most instances were
already correct.

-- 
Peter Eisentraut              http://www.2ndQuadrant.com/
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