[win32] PlatformDefs.h: Add forward declaration of SOCKET and SYSTEMTIME
[win32] Undef some win32 defines
HALManager.h: remove unused define
Mass remove of "system.h" from headers; add "PlatformConfig.h", "PlatfromDefs.h" to some headers/.cpp; add "system.h" to some .cpp, replace some macros

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