Add cubeb@62871b2 to Externals/

Includes submodule sanitizers-cmake@f09151b

Externals/cubeb/INSTALL.md

@@ -0,0 +1,24 @@
+# Build instructions for libcubeb
+
+You must have CMake v3.1 or later installed.
+
+1. `git clone --recursive https://github.com/kinetiknz/cubeb.git`
+2. `mkdir cubeb-build`
+3. `cd cubeb-build`
+3. `cmake ../cubeb`
+4. `cmake --build .`
+5. `ctest`
+
+# Windows build notes
+
+Windows builds can use Microsoft Visual Studio 2015 (the default) or MinGW-w64
+with Win32 threads (by passing `cmake -G` to generate the appropriate build
+configuration).  To build with MinGW-w64, install the following items:
+
+- Download and install MinGW-w64 with Win32 threads.
+- Download and install CMake.
+- Run MinGW-w64 Terminal from the Start Menu.
+- Follow the build steps above, but at step 3 run:
+  `cmake -G "MinGW Makefiles" ..`
+- Continue the build steps above.
+