The CI builds link against XAudio2_9, which isn't available on Windows 8
and lower. As a quick and dirty workaround, this commit ships the
XAudio2 redistributable on those older Windows versions. Simply renaming
the redistributable to XAudio2_9.dll isn't strictly allowed by the
documentation, but it works and is probably an acceptable hack to
support an outdated operating system...
Fixesarch1t3cht/Aegisub#16 .
VS 2015 has made distributing the dynamic CRT awful; the installer is
larger than Aegisub itself and app-local deployment requires an absurd
number of DLLs.
