The Win32 API has an InsertMenuItem macro, which (in your case) is
defined as

#define InsertMenuItem InsertMenuItemA

So every time you write InsertMenuItem anywhere in your source code, the
compiler systematically replaces that with InsertMenuItemA, without
thinking whether it's reasonable or not. That's why macros should be
'ALL_CAPITALS', not in 'TitleCase'.

Anyway, the workaround is:
#include <windows.h>
#undef InsertMenuItem

Tom