Add clang 3.8 builds.

.github/workflows/ci.yml

@@ -2,7 +2,7 @@ name: asio CI
 
 on:
   push:
-    branches: [ master, citest-*, github-actions-1 ]
+    branches: [ master, citest-* ]
 
 jobs:
   build:
@@ -277,6 +277,25 @@ jobs:
             separate-compilation: --enable-separate-compilation
             optim-level: -O0
           #
+          # Linux / clang++-3.8 -std=c++11 / -O2 / standalone
+          #
+          - build-type: full
+            runs-on: ubuntu-16.04
+            compiler: clang++-3.8
+            cxx-std: c++11
+            optim-level: -O2
+          #
+          # Linux / clang++-3.8 -std=c++11 / -O0 / boost 1.64 / separate compilation
+          #
+          - build-type: full
+            runs-on: ubuntu-16.04
+            compiler: clang++-3.8
+            cxx-std: c++03
+            separate-compilation: --enable-separate-compilation
+            optim-level: -O0
+            with-boost: --with-boost=$GITHUB_WORKSPACE/boost_1_64_0
+            boost-url: https://sourceforge.net/projects/boost/files/boost/1.64.0/boost_1_64_0.tar.bz2/download
+          #
           # macOS / c++2a -fcoroutines-ts / -O2 / standalone
           #
           - build-type: full