Change how init functions are written in the generated Go.
Change how init functions are written in the generated Go.

Now, all init statements will appear in a single init func
per file. No init function will be written if there are no
such statements.

golang/protobuf,tamird/protobuf-2,daemonl/protobuf,golang/protobuf,jrbarron/protobuf,aoeu/protobuf,fuchsia-mirror/third_party-github.com-golang-protobuf,jmptrader/protobuf-1,ekle/protoc-gen-goweb_test,mwitkow-io/protobuf,skyportsystems/go-protobuf,kung-foo/protobuf,ArtemTeleshev/go-protobuf,adnaan/protobuf,skyportsystems/go-protobuf,eduardiazf/protobuf,csuideal/protobuf,tamird/protobuf-2,jeremyletang/protobuf,alskjstl/protobuf,trdata/protobuf,qinlodestar/protobuf,fuchsia-mirror/third_party-github.com-golang-protobuf,francoishill/protobuf,ekle/protoc-gen-goweb,trdata/protobuf