Add missing dll export macros.

src/google/protobuf/compiler/plugin.h

@@ -64,7 +64,7 @@ namespace compiler {
 class CodeGenerator;    // code_generator.h
 
 // Implements main() for a protoc plugin exposing the given code generator.
-int PluginMain(int argc, char* argv[], const CodeGenerator* generator);
+LIBPROTOC_EXPORT int PluginMain(int argc, char* argv[], const CodeGenerator* generator);
 
 }  // namespace compiler
 }  // namespace protobuf

src/google/protobuf/compiler/subprocess.h

@@ -53,7 +53,7 @@ class Message;
 namespace compiler {
 
 // Utility class for launching sub-processes.
-class Subprocess {
+class LIBPROTOC_EXPORT Subprocess {
  public:
   Subprocess();
   ~Subprocess();

src/google/protobuf/generated_message_util.h

@@ -68,11 +68,11 @@ namespace internal {
 
 
 // Constants for special floating point values.
-double Infinity();
-double NaN();
+LIBPROTOBUF_EXPORT double Infinity();
+LIBPROTOBUF_EXPORT double NaN();
 
 // Constant used for empty default strings.
-extern const ::std::string kEmptyString;
+LIBPROTOBUF_EXPORT extern const ::std::string kEmptyString;
 
 
 }  // namespace internal

src/google/protobuf/repeated_field.h

@@ -305,7 +305,7 @@ class LIBPROTOBUF_EXPORT StringTypeHandlerBase {
   static void Merge(const string& from, string* to) { *to = from; }
 };
 
-class LIBPROTOBUF_EXPORT StringTypeHandler : public StringTypeHandlerBase {
+class StringTypeHandler : public StringTypeHandlerBase {
  public:
   static int SpaceUsed(const string& value)  {
     return sizeof(value) + StringSpaceUsedExcludingSelf(value);