xerrni

Results 3 issues of xerrni

First commit fixes ccls hanging in MultiQueueWaiter destructor during test execution. Second one enables tests execution when clang version >= 6.0.0.

I have tried compiling RcloneBrowser on: `Linux ubuntu 4.4.0-64-generic #85-Ubuntu SMP Mon Feb 20 11:50:30 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux` Installed QT 5.8, some command line output: ``` xerrni@ubuntu:~/Downloads/RcloneBrowser/RcloneBrowser/build/build$...

Currently when project is created a `POST` request is sent. Response for this request is sent after input is downloaded. In my opinion it is wrong user experience as download...

enhancement