update memdep when an instruction is deleted.  This code isn't actually reached in the testcase in PR8954, but it's safe and good practice.
update memdep when an instruction is deleted.  This code isn't
actually reached in the testcase in PR8954, but it's safe and good
practice.



git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@123224 91177308-0d34-0410-b5e6-96231b3b80d8

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