go/ssa: add DebugRef.Object

This function is in the documentation for *ssa.DebugRef but is not defined anywhere, so define it now.

Change-Id: I0a6c07ccac16851541a5fe337f0bba66608949cb
GitHub-Last-Rev: 30f39663b48acd419a9ae8a90ae34d9350aff218
GitHub-Pull-Request: golang/tools#201
Reviewed-on: https://go-review.googlesource.com/c/tools/+/216477
Reviewed-by: Alan Donovan <adonovan@google.com>
Reviewed-by: Robert Findley <rfindley@google.com>
diff --git a/go/ssa/ssa.go b/go/ssa/ssa.go
index 78272c5..4dfdafd 100644
--- a/go/ssa/ssa.go
+++ b/go/ssa/ssa.go
@@ -1478,6 +1478,8 @@
 func (c *NamedConst) Package() *Package                    { return c.pkg }
 func (c *NamedConst) RelString(from *types.Package) string { return relString(c, from) }
 
+func (d *DebugRef) Object() types.Object { return d.object }
+
 // Func returns the package-level function of the specified name,
 // or nil if not found.
 //