Major updates to dependencies and build compatibility

[kth5]

Featuring:

• support with macOS Sierra/Xcode 8.0
• support for Cygwin based MinGW builds
• majority of packages updated
• update to latest available version of spotify's lib
• likely fixed a showstopping bug for the Windows build :)

I opened a PR a while ago already and apparently it was a bit hasty as I broke the Windows build even more. I took some time working out the Windows stuff and have a working build now with only a few minor quirks that depend on the build environment.

Before I open a PR, I would like to see a branch to merge this to:

https://github.com/kth5/Dependencies

Since I was fiddling with a MinGW specific problem regarding pthreads emulation on Windows, I ended up building on Cygwin with a mingw target as well and added basic support for this as well. There are a few quirks to this though and a build should be run like so:

make build=x86_64-pc-cygwin qtplatform=cygwin-g++

Qt won't chose the correct environment properly and if --build is not set on configure, it'll break a few things on the way (protobuf executing its own protoc.exe for instance).

All files are in my Google drive again as linked in downloader/downloader.py.

Also, no PR for Clementine itself yet since a few updates to dist/windows/clementine.nsi are needed to pick up new DLL versions.