Zstandard support for setup

[Jon Turney]

On 10/10/2018 19:36, Achim Gratz wrote:
> Jon Turney writes:
>> This should check for ztd in configure.ac using PKG_CHECK_MODULES,
>> rather than just assuming -lzstd is going to work.
> 
> Done.
> 
>> + using namespace std;
>>
>> Please don't
> 
> Done.
> 
> https://repo.or.cz/cygwin-setup/local.git/patch/fff4b1448072efe5ebb6549cfe04bc15344a3973

Applied.

I removed the commented out logging, updated build instructions and 
build prerequisites installed in CI

Thanks.

>> compress_zstd.h:
>>
>> +/* this is the parent class for all compress IO operations.
>> + */
>>
>> Comment is incorrect
> 
> Done in the above, additionally remove the same copy&paste comment from
> two existing files:
> 
> https://repo.or.cz/cygwin-setup/local.git/patch/abf5afbfce47d1942f6d4c2f62fc8b1566920e2e

Applied.