debug/dwarf: add an Offset field to CommonType, containing the DWARF offset of the type's entry.

Change-Id: I28736cd018ae6e19e429388dd681a02c1c604062
Reviewed-on: https://go-review.googlesource.com/10478
Reviewed-by: jcd . <jcd@golang.org>
diff --git a/dwarf/type.go b/dwarf/type.go
index 1c3223a..134231f 100644
--- a/dwarf/type.go
+++ b/dwarf/type.go
@@ -28,6 +28,7 @@
 	ByteSize    int64        // size of value of this type, in bytes
 	Name        string       // name that can be used to refer to type
 	ReflectKind reflect.Kind // the reflect kind of the type.
+	Offset      Offset       // the offset at which this type was read
 }
 
 func (c *CommonType) Common() *CommonType { return c }
@@ -789,6 +790,8 @@
 		goto Error
 	}
 
+	typ.Common().Offset = off
+
 	{
 		b, ok := e.Val(AttrByteSize).(int64)
 		if !ok {