Clarify jsonpb package docs.

jsonpb/jsonpb.go

diff --git a/jsonpb/jsonpb.go b/jsonpb/jsonpb.go
index 57b58fd..4c22d21 100644
--- a/jsonpb/jsonpb.go
+++ b/jsonpb/jsonpb.go
@@ -30,12 +30,11 @@
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 /*
-Package jsonpb provides marshaling/unmarshaling functionality between
-protocol buffer and JSON objects.
+Package jsonpb provides marshaling and unmarshaling between protocol buffers and JSON.
+It follows the specification at https://developers.google.com/protocol-buffers/docs/proto3#json.
 
-Compared to encoding/json, this library:
- - encodes int64, uint64 as strings
- - optionally encodes enums as integers
+This package produces a different output than the standard "encoding/json" package,
+which does not operate correctly on protocol buffers.
 */
 package jsonpb
 

protoc-gen-go/generator/generator.go

diff --git a/protoc-gen-go/generator/generator.go b/protoc-gen-go/generator/generator.go
index c2c96bf..0f7a337 100644
--- a/protoc-gen-go/generator/generator.go
+++ b/protoc-gen-go/generator/generator.go
@@ -2541,7 +2541,9 @@
 	w.Close()
 	b = buf.Bytes()
 
-	g.P("var fileDescriptor", file.index, " = []byte{")
+	v := fmt.Sprintf("fileDescriptor%d", file.index)
+	g.P()
+	g.P("var ", v, " = []byte{")
 	g.In()
 	g.P("// ", len(b), " bytes of a gzipped FileDescriptorProto")
 	for len(b) > 0 {