add some preprocessor defines to make checks easy

turns

    #if (CC_TARGET_PLATFORM == CC_PLATFORM_IOS) || (CC_TARGET_PLATFORM == CC_PLATFORM_ANDROID && AVALON_PLATFORM_FLAVOR == AVALON_PLATFORM_FLAVOR_AMAZON)
    // ...
    #endif

into


    #if AVALON_PLATFORM_IS_IOS || AVALON_PLATFORM_IS_ANDROID_AMAZON
    // ...
    #endif