Use DefaultDllImportSearchPathsAttribute (#66)
Use DefaultDllImportSearchPathsAttribute (#66)

Fixes #64

Context: https://devdiv.visualstudio.com/DevDiv/_workitems/edit/1139578
Context: https://liquid.microsoft.com/Web/Object/Read/ms.security/Requirements/Microsoft.Security.SystemsADM.10039#guide

The current security guidance is that the [`System.Runtime.InteropServices.DefaultDllImportSearchPathsAttribute`](https://docs.microsoft.com/en-us/dotnet/api/system.runtime.interopservices.defaultdllimportsearchpathsattribute?view=netcore-3.1)
attribute should be placed either on the assembly or on `[DllImport]`
methods, to control and constrain where [`LoadLibraryEx()`](https://docs.microsoft.com/en-us/windows/win32/api/libloaderapi/nf-libloaderapi-loadlibraryexa?redirectedfrom=MSDN)
will look for native libraries.

This commit implements this in the `Native.cs` file. We are using
an assembly level atribute but place it in the area where all the
native calls are maintained.
grendello/LibZipSharp