Nirbheek Chauhan authored Apr 19, 2016 and Tim-Philipp Müller committed Aug 18, 2016

D3DX has been deprecated for the last 4 years and latest versions of
Windows no longer ship headers for it. This is fine as long as you're
building with Cerbero's Wine-based DirectX headers, but sucks if you
want to build against the actual Windows SDK.

We were just using it to get error strings anyway, so just use the
generic error string API.