scripts:Add includes to extension helper

Generated extension helper has dependencies on vulkan.h and
utility (for std::pair) that weren't declared.
diff --git a/scripts/helper_file_generator.py b/scripts/helper_file_generator.py
index 5aa8dee..530a833 100644
--- a/scripts/helper_file_generator.py
+++ b/scripts/helper_file_generator.py
@@ -558,6 +558,9 @@
         extension_helper_header += '#ifndef VK_EXTENSION_HELPER_H_\n'
         extension_helper_header += '#define VK_EXTENSION_HELPER_H_\n'
         struct  = '\n'
+        extension_helper_header += '#include <vulkan/vulkan.h>\n'
+        extension_helper_header += '#include <utility>\n'
+        extension_helper_header += '\n'
         extension_dict = dict()
         for type in ['Instance', 'Device']:
             if type == 'Instance':