README for C++ codebase

The C++ codebase will eventually be the primary sound generation module
for this app. It's still experimental, and not yet wired up to the Android
parts, but can be used to make sound. The best way is to use the simple
test app for the Mac.

To build, edit src/SynthApp/SynthMain.mm to change the path to ROM1A.SYX
to the actual path. These patches can be downloaded from:

http://www.abdn.ac.uk/~mth192/dx7/dx7patch.zip

Also change the "KeyRig 49" string to match the actual USB name of your
MIDI controller. Then "open src/SynthApp.xcodeproj", then do "Build and
Run".

The File Open menu command is hooked up as well and will load SYX format
DX7 patch files (32 patches per file). Send program change midi events
with the first 32 program numbers.