Update PPAPI IDL generator to define versioned structs, and unversioned typedef.

ppapi/thunk/ppb_scrollbar_thunk.cc

Index: ppapi/thunk/ppb_scrollbar_thunk.cc
diff --git a/ppapi/thunk/ppb_scrollbar_thunk.cc b/ppapi/thunk/ppb_scrollbar_thunk.cc
index c0ab39ced72f0136c18e29e86674c07088a18fdd..09f0677f5bda657e2b11743bd66da419b2f67967 100644
--- a/ppapi/thunk/ppb_scrollbar_thunk.cc
+++ b/ppapi/thunk/ppb_scrollbar_thunk.cc
@@ -87,7 +87,7 @@ const PPB_Scrollbar_Dev g_ppb_scrollbar_thunk = {
 
 }  // namespace
 
-const PPB_Scrollbar_Dev* GetPPB_Scrollbar_Dev_Thunk() {
+const PPB_Scrollbar_Dev_0_5* GetPPB_Scrollbar_Dev_0_5_Thunk() {
   return &g_ppb_scrollbar_thunk;
 }