See if clang 7 works

Author: henryiii

.travis.yml

@@ -55,11 +55,11 @@ matrix:
   - services: docker
     env: PYTHON=3.6 CPP=17 GCC=7
   - os: linux
-    env: PYTHON=3.6 CPP=17 CLANG=5.0
+    env: PYTHON=3.6 CPP=17 CLANG=7
     addons:
       apt:
-        sources: [deadsnakes, llvm-toolchain-trusty-5.0, ubuntu-toolchain-r-test]
-        packages: [python3.6-dev python3.6-venv clang-5.0 llvm-5.0-dev, lld-5.0]
+        sources: [deadsnakes, llvm-toolchain-trusty-7, ubuntu-toolchain-r-test]
+        packages: [python3.6-dev python3.6-venv clang-7 llvm-7-dev, lld-7]
   - os: osx
     osx_image: xcode7.3
     env: PYTHON=2.7 CPP=14 CLANG CMAKE=1
@@ -163,13 +163,13 @@ install:
         libeigen3-dev libboost-dev cmake make ${EXTRA_PACKAGES} && break; done"
   else
 
-    if [ "$CLANG" = "5.0" ]; then
+    if [ "$CLANG" = "7" ]; then
       if ! [ -d ~/.local/include/c++/v1 ]; then
-        # Neither debian nor llvm provide a libc++ 5.0 deb; luckily it's fairly quick
+        # Neither debian nor llvm provide a libc++ 5.1 deb; luckily it's fairly quick
         # to build, install (and cache), so do it ourselves:
         git clone --depth=1 https://github.com/llvm-mirror/llvm.git llvm-source
-        git clone https://github.com/llvm-mirror/libcxx.git llvm-source/projects/libcxx -b release_50
-        git clone https://github.com/llvm-mirror/libcxxabi.git llvm-source/projects/libcxxabi -b release_50
+        git clone https://github.com/llvm-mirror/libcxx.git llvm-source/projects/libcxx -b release_70
+        git clone https://github.com/llvm-mirror/libcxxabi.git llvm-source/projects/libcxxabi -b release_70
         mkdir llvm-build && cd llvm-build
         cmake -DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_PREFIX=~/.local ../llvm-source
         make -j2 install-cxxabi install-cxx