Canged CodedInputStream.ReadTag to use boolean result with out params to
support reading a field name rather than a field tag.
diff --git a/src/ProtocolBuffers.Test/TestProtos/UnitTestXmlSerializerTestProtoFile.cs b/src/ProtocolBuffers.Test/TestProtos/UnitTestXmlSerializerTestProtoFile.cs
index 722a5ff..1b523c3 100644
--- a/src/ProtocolBuffers.Test/TestProtos/UnitTestXmlSerializerTestProtoFile.cs
+++ b/src/ProtocolBuffers.Test/TestProtos/UnitTestXmlSerializerTestProtoFile.cs
@@ -325,7 +325,7 @@
         while (input.ReadTag(out tag, out field_name)) {

           switch (tag) {

             case 0: {

-              throw InvalidProtocolBufferException.InvalidTag();

+              throw pb::InvalidProtocolBufferException.InvalidTag();

             }

             default: {

               if (pb::WireFormat.IsEndGroupTag(tag)) {

@@ -569,7 +569,7 @@
         while (input.ReadTag(out tag, out field_name)) {

           switch (tag) {

             case 0: {

-              throw InvalidProtocolBufferException.InvalidTag();

+              throw pb::InvalidProtocolBufferException.InvalidTag();

             }

             default: {

               if (pb::WireFormat.IsEndGroupTag(tag)) {

@@ -830,7 +830,7 @@
             while (input.ReadTag(out tag, out field_name)) {

               switch (tag) {

                 case 0: {

-                  throw InvalidProtocolBufferException.InvalidTag();

+                  throw pb::InvalidProtocolBufferException.InvalidTag();

                 }

                 default: {

                   if (pb::WireFormat.IsEndGroupTag(tag)) {

@@ -1209,7 +1209,7 @@
         while (input.ReadTag(out tag, out field_name)) {

           switch (tag) {

             case 0: {

-              throw InvalidProtocolBufferException.InvalidTag();

+              throw pb::InvalidProtocolBufferException.InvalidTag();

             }

             default: {

               if (pb::WireFormat.IsEndGroupTag(tag)) {

@@ -1630,7 +1630,7 @@
         while (input.ReadTag(out tag, out field_name)) {

           switch (tag) {

             case 0: {

-              throw InvalidProtocolBufferException.InvalidTag();

+              throw pb::InvalidProtocolBufferException.InvalidTag();

             }

             default: {

               if (pb::WireFormat.IsEndGroupTag(tag)) {