Make library work with OpenBSD

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On OpenBSD I got the following error message:

PC=0x0 m=0 sigcode=1 addr=0x0
signal arrived during cgo execution

goroutine 1 gp=0xc000002540 m=0 mp=0x352b40 [syscall]:
runtime.cgocall(0x348e20, 0xc000051eb8)
        /usr/local/go/src/runtime/cgocall.go:167 +0x56 fp=0xc000051e90 sp=0xc000051e58 pc=0x324a56
github.com/jkl1337/go-mediainfo._Cfunc_g_MediaInfo_New()
        _cgo_gotypes.go:211 +0x47 fp=0xc000051eb8 sp=0xc000051e90 pc=0x347bc7
github.com/jkl1337/go-mediainfo.New()
...

Using the static variant of the library (MediaInfoDLL/MediaInfoDLL_Static.h instead of MediaInfoDLL/MediaInfoDLL.h) seems to solve the issue. Instead of copying the header file in the Repository, I am now including the installed header file. Unfortunately I'm not familiar enough with C to understand why this works and the dynamic variant didn't.

I have also added the additional paths needed to find the library on OpenBSD.

I have tested successfully on Linux and OpenBSD, but don't have access to a Darwin machine.