Fix linking error under Win 7 - do not import MinCore_Downlevel.lib if target is Win 7 or earlier.

Applied in PR3243 to 2.4 branch.

modules/videoio/src/cap_msmf.cpp

@@ -78,7 +78,9 @@
 #pragma comment(lib, "mfuuid")
 #pragma comment(lib, "Strmiids")
 #pragma comment(lib, "Mfreadwrite")
+#if (WINVER >= 0x0602) // Available since Win 8
 #pragma comment(lib, "MinCore_Downlevel")
+#endif
 
 #include <mferror.h>