BUG: protoc-gen-gogofast not generate trailing comments

[hitzhangjie]

for example, here's the protobuf:

syntax="proto3";
package hello;
...
message HelloRequest {
    // xxx111
    string msg = 1; // xxx222
}

Then execute the: protoc --gogofast_out=. hello.proto, the generated code is:

type HelloRequest struct {
    // xxx111
    Msg                  string   `protobuf:"bytes,1,opt,name=msg,proto3" json:"msg,omitempty"`                                                                        
    XXX_NoUnkeyedLiteral struct{} `json:"-"`
    XXX_unrecognized     []byte   `json:"-"`
    XXX_sizecache        int32    `json:"-"`
}

We could see, the trailing comments is not generated, while protoc-gen-go will handle both the leading and trailing comments. Please support this style of trailing comments.

This style of trailing comments will help align the fields, much clearer. It will improve readability. I won't have to switch between the *.pb.go and *.proto file.