TIP 381 memleaks

From the checkin [2778ad161a] that implemented
TIP 381, there's been memleaks reported by the
test suite:

==== oo-call-1.18 object call introspection - memory leaks FAILED
==== Contents of test case:

leaktest {
info object call oo::object destroy
}

---- Result was:
230
---- Result should have been (exact matching):
0
==== oo-call-1.18 FAILED

==== oo-call-2.13 class call introspection - memory leaks FAILED
==== Contents of test case:

leaktest {
info class call oo::class destroy
}

---- Result was:
230
---- Result should have been (exact matching):
0
==== oo-call-2.13 FAILED

==== oo-call-3.2 current call introspection FAILED
==== Contents of test case:

oo::class create A {
superclass root
method x {} {self call}
}
oo::class create B {
superclass A
method x {} {self call;next}
}
B create y
oo::objdefine y method x {} {self call;next}
leaktest {
y x
}

---- Result was:
1737
---- Result should have been (exact matching):
0
==== oo-call-3.2 FAILED