Avoid Windows 8 Getversion deprecated errors.

Windows 8 SDKs complain that GetVersion() is deprecated.

We only use GetVersion like this:

	(GetVersion() < 0x80000000)

which checks if the Windows version is NT based. Use a macro check_winnt()
which uses GetVersion() on older SDK versions and true otherwise.
(cherry picked from commit a4cc3c8041)

crypto/cryptlib.c

@@ -909,7 +909,7 @@ void OPENSSL_showfatal (const char *fmta,...)
 
 #if defined(_WIN32_WINNT) && _WIN32_WINNT>=0x0333
     /* this -------------v--- guards NT-specific calls */
-    if (GetVersion() < 0x80000000 && OPENSSL_isservice() > 0)
+    if (check_winnt() && OPENSSL_isservice() > 0)
     {	HANDLE h = RegisterEventSource(0,_T("OPENSSL"));
 	const TCHAR *pmsg=buf;
 	ReportEvent(h,EVENTLOG_ERROR_TYPE,0,0,0,1,0,&pmsg,0);