eliminate MINGW pragma warning
Merge pull request #2092 from alalek:fix_mingw_warn
fixed bug #3341
SSE2 optimization of cv::remap doesn't work with big images
Merge pull request #2086 from ilya-lavrenov:mul_fix
Fixed MinGW build by declaring the minimal required Windows version.

Also deleted miscellaneous remaining multimon cruft.
Deleted #include <winuser.h>, because <windows.h> includes it
already.

This should have a nice side effect of preventing us from
accidentally using any Windows API that's too new.
Merge pull request #2087 from ilya-lavrenov:remap_sse2_cond
Merge pull request #2094 from SpecLad:multimon-be-gone
fixed bug #3319
Merge pull request #2084 from ilya-lavrenov:cont