Update for Visual Studio solutions

[Zuzu-Typ]

This pull request includes the following changes:

• added support for building dynamic libraries (DLLs)
• added Debug-NoHTTP configuration (+ a DLL version of every configuration)
• added include directories and additional library paths (for ogg and opus)
• added libogg.props (from vorbis)

Note#1: Merging this only makes sense, if https://github.com/xiph/ogg/pull/29 is merged, because the solution searches for libogg.lib (instead of libogg_static.lib) in the respective *DLL subfolder if opus is built dynamically. This can be changed of course, however it only makes sense to me this way

Note#2: This has not been tested with openssl, which I was unable to build successfully (it may or may not require additional include directories and / or library paths).

[rillian]

Parts of this, like the def file, should definitely be merged, but I'm not confident I can update the patch properly.

[mattgwwalker]

I would love to be able to compile x64 Windows DLLs for OpusFile. It seems Zuzu-Typ had done all the work to get the Visual Studio project working back in 2017, but this wasn't accepted.

It looks like GitHub's interface is saying that Zuzu-Typ's repository with the changes has been deleted (it's labelled an "unknown repository").

Is there a recommended way to compile OpusFile for Windows?

[rillian]

For other opus libraries, people have contributed cmake build configurations, which would be the preferred way to build it, except no one has done that for opusfile yet.

Note that our code integrating the Windows certificate store is currently broken; you'd need to find a work-around for that if you want to use the https support.