LDC 1.15.0-beta2

[kinke]

Glad to announce the second beta for LDC 1.15, with these changes 
compared to beta1 
(https://forum.dlang.org/thread/wavjrnwlxkkpzkqjvzjr@forum.dlang.org):

* Based on current DMD stable.
* LLVM for prebuilt packages upgraded to v8.0.0 final.
* Fixed beta1 regression: prebuilt Linux x86_64 package is usable 
with older linkers again (e.g., on Ubuntu 14.04).
* Fixed beta1 regression: dcompute is usable again.
* Prebuilt packages don't depend on libtinfo and libedit anymore.

Full release log and downloads: 
https://github.com/ldc-developers/ldc/releases/tag/v1.15.0-beta2

Please help test, and thanks to all contributors!