Add a LiveRangeQuery class.
Add a LiveRangeQuery class.

This class is meant to be the primary interface for examining a live
range in the vicinity on a given instruction. It avoids all the messy
dealings with iterators and early clobbers.

This is a more abstract interface to live ranges, hiding the
implementation as a vector of segments.

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@157141 91177308-0d34-0410-b5e6-96231b3b80d8

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