windows: Replace Q_OS_WIN with Q_OS_WIN_TODO so we can start porting

Now it builds. This way I can port each Q_OS_WIN one by one and make
sure everything still builds, without risking breaking Linux/macOS.

src/Config.cpp

@@ -226,7 +226,7 @@ void Config::setInternalFlags(InternalFlags flags)
 
 void Config::Private::fixFlags()
 {
-#if defined(Q_OS_WIN)
+#if defined(Q_OS_WIN_TODO)
     if (QOperatingSystemVersion::current().majorVersion() < 10) {
         // Aero-snap requires Windows 10
         m_flags = m_flags & ~Flag_AeroSnapWithClientDecos;
@@ -258,7 +258,7 @@ void Config::Private::fixFlags()
     }
 #endif
 
-#if (!defined(Q_OS_WIN) && !defined(Q_OS_MACOS))
+#if (!defined(Q_OS_WIN_TODO) && !defined(Q_OS_MACOS))
     // QtQuick doesn't support AeroSnap yet. Some problem with the native events not being received...
     m_flags = m_flags & ~Flag_AeroSnapWithClientDecos;
 #endif