Unify the destruction code used for node pairs vs normal nodes.  This was causing a problem before because global values with incoming edges didn't copy the incoming edges to the node they were being merged from, causing the poolalloc pass to die.
Unify the destruction code used for node pairs vs normal nodes.  This was
causing a problem before because global values with incoming edges didn't
copy the incoming edges to the node they were being merged from, causing
the poolalloc pass to die.


git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@2079 91177308-0d34-0410-b5e6-96231b3b80d8

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