Move most CI scripts in scripts/ci ...

The root directory was getting a bit crowded.
semaphore-ci.sh was not moved, because there's no visible way to configure semaphore from the repository.
Additionally, build.d is left in the root directory as it's useful to have it here,
and it'll be only one script one build.sh, build.cmd, and build-gdc.sh are gone.

Update LDC/DMD to the latest version

Remove workaround in Travis-CI config ...

The installer has long been able to install dub independently.
The CI was already aware of this, as it was using the comma-separated syntax.
This extends the usage of it to all matrix elements and remove the duplication.

FIX

Update Travis distribution to Bionic ...

Trusty is EOL already. The default nowadays is Xenial, but Bionic is available,
so we might as well go for it.
Additionally, 'sudo:false' has been removed as it is the default and is considered deprecated.

Reduce number of tested versions on Travis + use latest dub

[.travis.yml]: Bump latest test compiler to dmd-2.088.1

Bump CI versions to 2.076.0

Bump deployment to LDC 1.15.0

Fix LDC versions for the deployment stage

Build win{32,64} binaries with LDC

Merge pull request #1520 from wilzbach/semaphore-gdc ...

Use GDC from Semaphore and upgrade the minimally required host compiler

Use GDC from Semaphore and upgrade the minimally required host compiler

Only update the LATEST file for stable releases (i.e. ignore -alpha, -beta and -rc) (#1521) ...

* Only update the LATEST file for stable releases (i.e. ignore -alpha,
-beta and -rc)

Tested with `travis-conditions`:

https://docs.travis-ci.com/user/conditions-testing

$ travis-conditions "tag =~ ^v\d+\.\d+\.\d+[^-]*\$" --data '{"tag": "v1.11.0-alpha.1"}'
false
$ travis-conditions "tag =~ ^v\d+\.\d+\.\d+[^-]*\$" --data '{"tag": "v1.11.0"}'
true
$ travis-conditions "tag =~ ^v\d+\.\d+\.\d+[^-]*\$" --data '{"tag": "v1.11.0+896429d"}'
true

Also see https://semver.org/#spec-item-9

Merge remote-tracking branch 'upstream/stable' into merge_stable

Merge remote-tracking branch 'upstream/stable' into merge_stable

Use -flto=full for the release builds

Install the newest version of dub to avoid random network failures

Fix #1419 - Use LDC by default

[auto-deploy] search for 32-bit DMD executable

Remove on:master from the Travis stage conditions

Use DMD for now for pretty stacktraces

Add automatic GH deployment for Linux 32/64 and OSX 64

fix broken env var config ...

- shouldn't have been a nested array
- suprisingly still worked, but was incorrectly parsed

Bump versions to 2.078.0

Update compiler support ...

- Add testing for DMD 2.076.1
- Update frontend versions for dmd-beta and dmd-nightly
- Test on LDC 1.4.0 and 1.5.0
- Stop testing on LDC 0.17.2
- Stop testing on DMD 2.067.1

Drop CI support for the DMD 2.066.1 frontend.

Update travis compilers

run dub with other compilers for test coverage

add libevent dependency for travis

Update .travis.yml