Remove testing & support for really old clang <= 3.8.

The old clangs have problems with the Lyra library and SFINAE. To avoid increased development time to workarounds dropping support for them.

Author: grafikrobot

README.adoc

@@ -16,7 +16,7 @@ Continuously tested on:
 
 * FreeBSD Clang 11, 12, 13, 14, 15, 16, 17, 18, 19
 * FreeBSD 10, 11, 12, 13, 14
-* Linux Clang 3.6, 3.7, 3.8, 3.9, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19
+* Linux Clang 3.9, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19
 * Linux GCC 4.8, 4.9, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14
 * macOS Xcode 14.1, 14.2, 14.3.1, 15.4, 16.0
 * Windows MinGW 8.1.0

azure-pipelines.yml

@@ -272,9 +272,9 @@ stages:
         Clang 5: {CXX: clang++-5.0, TOOLSET: clang-5.0, PACKAGES: clang-5.0, LLVM_VER: 5.0, LLVM_OS: 'bionic', CONTAINER: "ubuntu_1804"}
         Clang 4: {CXX: clang++-4.0, TOOLSET: clang-4.0, PACKAGES: clang-4.0, LLVM_VER: 4.0, LLVM_OS: 'xenial', CONTAINER: "ubuntu_1604"}
         Clang 3.9: {CXX: clang++-3.9, TOOLSET: clang-3.9, PACKAGES: clang-3.9, LLVM_VER: 3.9, LLVM_OS: 'xenial', CONTAINER: "ubuntu_1604"}
-        Clang 3.8: {CXX: clang++-3.8, TOOLSET: clang-3.8, PACKAGES: clang-3.8, LLVM_VER: 3.8, LLVM_OS: 'xenial', CONTAINER: "ubuntu_1604"}
-        Clang 3.7: {CXX: clang++-3.7, TOOLSET: clang-3.7, PACKAGES: clang-3.7, CONTAINER: "ubuntu_1604"}
-        Clang 3.6: {CXX: clang++-3.6, TOOLSET: clang-3.6, PACKAGES: clang-3.6, CONTAINER: "ubuntu_1604"}
+        # Clang 3.8: {CXX: clang++-3.8, TOOLSET: clang-3.8, PACKAGES: clang-3.8, LLVM_VER: 3.8, LLVM_OS: 'xenial', CONTAINER: "ubuntu_1604"}
+        # Clang 3.7: {CXX: clang++-3.7, TOOLSET: clang-3.7, PACKAGES: clang-3.7, CONTAINER: "ubuntu_1604"}
+        # Clang 3.6: {CXX: clang++-3.6, TOOLSET: clang-3.6, PACKAGES: clang-3.6, CONTAINER: "ubuntu_1604"}
     pool:
       vmImage: 'ubuntu-20.04'
     container: $[ variables['CONTAINER'] ]