* Add ubuntu cosmic to Ubuntu supported releases

* Make CMake find_package(Clang) work. Fixes upstream bug
  https://bugs.llvm.org/show_bug.cgi?id=37128
  - Move Clang*.cmake back to /usr/lib/llvm-X.Y/lib/cmake/clang and install a
    symlink in /usr/lib/cmake/clang-X.Y.
  - Ensure that the LLVM installation prefix is correctly discovered despire
    symlinks (replaces fix-cmake-config-prefix.diff).
  - Create /usr/lib/llvm-X.Y/bin/clang-X.Y symlink as required by
    ClangTargets-relwithdebinfo.cmake.
  - Remove useless LLVM_CMAKE_DIR sed command that did not match anything.
  - Ignore missing binaries in ClangTargets-relwithdebinfo.cmake.

qualify-clang: improve CMake test

See merge request !3

* Explicitly check that both the default CMake find_package and the
  explicit version-specific check works as intended.
* Set CC/CXX to avoid requiring an additional compiler to be installed.
* Add comment to workaround objc test failure on Ubuntu 14.04 and 16.04.

Make Clang cmake files more usable

See merge request !2

# Conflicts:
#   debian/changelog

* Move Clang*.cmake back to /usr/lib/llvm-X.Y/lib/cmake/clang and
  install a symlink in /usr/lib/cmake/clang-X.Y to ensure that CMake can
  still find it.
* Ensure that the LLVM installation prefix is correctly discovered
  despire symlinks (replaces fix-cmake-config-prefix.diff).
* Create /usr/lib/llvm-X.Y/bin/clang-6.0 symlink as required by
  ClangTargets-relwithdebinfo.cmake.
* Remove useless LLVM_CMAKE_DIR sed command that did not match anything.
* Ignore missing binaries in ClangTargets-relwithdebinfo.cmake.
* Add regression test to qualify-clang.sh.

This reverts commit 6a1b120e.

* Fix a typo in the debci