[opus] libopusfile

[Timothy B. Terriberry]

Diego Elio Pettenò wrote:
> If you want autotools, it'll take just a few hours, so I can do that
> tomorrow night if it's okay with you; as long as you don't expect
> auto-version from git as that stuff seems to be the big problem even
> with opus :/

I know Ralph has argued that we should use the GNU make Makefile as the 
default build system. My personal opinion is that we should provide what 
people find useful (Windows project files would also be welcome for that 
reason).