File Associations (Apple), OPL2 Fixes (Apple)

(Sorry for two pulls in one request, it wouldn't let me make two separate ones? -Tres)

Closes #665 by adding working file association support for Apple.
Closes #693 by fixing OPL2 compilation for Apple.

#665 Changes include:
- Added new ${VARS} to CMakeList.txt:
   - site URL
   - project icon (mmpz)
   - mimetype prefix identifier (net.sourceforge.lmms)
- Rewrite of Info.plist file based on working examples from VLC and KeyPassX.

#665 Changes include:
- stricter opl2 code styling (fmopl.c)
- remove custom `INLINE` function declarations for __clang__ compilers


#693 Screenshot
![image](https://cloud.githubusercontent.com/assets/6345473/2911395/92cda9bc-d65a-11e3-9cf0-2d1dfebbea77.png)

#693 Screenshot
![image](https://cloud.githubusercontent.com/assets/6345473/2919632/34a3ae9e-d6dd-11e3-994a-102093cb6983.png)