Improve efficiency of CoalesceDuplicateStmts() by avoiding the revisitation of already processed subtrees.  Because the real performance bottle-neck is finding debugging info from binutils, this is a 'moral victory' rather than a real performance improvement.
Improve efficiency of CoalesceDuplicateStmts() by avoiding the revisitation of already processed subtrees.  Because the real performance bottle-neck is finding debugging info from binutils, this is a 'moral victory' rather than a real performance improvement.

zcth428/hpctoolkit111,HPCToolkit/hpctoolkit,zcth428/hpctoolkit,zcth428/hpctoolkit111,zcth428/hpctoolkit111,zcth428/hpctoolkit111,zcth428/hpctoolkit,zcth428/hpctoolkit,HPCToolkit/hpctoolkit,zcth428/hpctoolkit,zcth428/hpctoolkit,HPCToolkit/hpctoolkit,HPCToolkit/hpctoolkit,HPCToolkit/hpctoolkit,HPCToolkit/hpctoolkit,zcth428/hpctoolkit111