Fix some header includes

Errors arose with gcc 7.3

src/generator/generator.cpp

@@ -37,12 +37,6 @@
 #include <google/protobuf/io/zero_copy_stream.h>
 #include <google/protobuf/descriptor.h>
 
-#include <algorithm>
-#include <unordered_map>
-#include <vector>
-#include <sstream>
-#include <string>
-#include <list>
 
 using namespace ::qtprotobuf::generator;
 using namespace ::google::protobuf;

src/generator/protobufclassgenerator.cpp

@@ -26,6 +26,7 @@
 #include "protobufclassgenerator.h"
 #include "utils.h"
 
+#include <iostream>
 #include <google/protobuf/descriptor.h>
 #include <google/protobuf/io/zero_copy_stream.h>
 

src/generator/utils.h

@@ -30,6 +30,7 @@
 #include <sstream>
 #include <unordered_map>
 #include <list>
+#include <algorithm>
 
 namespace google { namespace protobuf {
 class FileDescriptor;