LDC 1.17.0

[kinke]

Glad to announce LDC 1.17:

* Based on D 2.087.1.
   * The DMD fix wrt. 'local templates can now receive local 
symbols' hasn't been ported yet.
* LLVM upgraded to v8.0.1.
* Fix for v1.16.0 regression when returning void expressions.
* Init symbols, TypeInfos and vtables of non-exported aggregates 
are now hidden with `-fvisibility=hidden`.
* Don't ignore some options like `-lowmem` in response files.
* Proper Unicode support for LDC/LDMD itself on Windows.
* More fixes...

Full release log and downloads: 
https://github.com/ldc-developers/ldc/releases/tag/v1.17.0

Thanks to all contributors!