[opus] [libopusfile PATCH] build: implement autotools build system for libopusfile. (v4)

[Timothy B. Terriberry]

Diego Elio Pettenò wrote:
> Everything looks good to me, although
>
>> +  [enable_doc=$enableval], [enable_doc=yes]
>
> could be ",, enable_doc=yes" for consistency.

Fixed.

I also made the dist format changes, fixed the debug target to no longer 
require the now-nonexistent example target, and added git-version.sh to 
EXTRA_DIST.

Committed as
https://git.xiph.org/?p=opusfile.git;h=9391feca516a;a=commitdiff

(the build bot will fail for a bit because doc/Doxyfile is now gone and 
it was building the documentation using that manually)