Trying to run C++17 on Travis.

.travis.yml

@@ -31,17 +31,18 @@ matrix:
     - script: make individual_tests
       env:
       - NDEBUG=0
-      - CPLUSPLUS=clang++-3.8
-      compiler: "clang++-3.8, Job: make individual_tests"
+      - CPLUSPLUS=clang++-6.0
+      compiler: "clang++-6.0, Job: make individual_tests"
       os: linux
       addons:
         apt:
           sources:
             - ubuntu-toolchain-r-test  # `apt-get` on Travis fails to install `clang-3.6 gnuplot` w/o this.
-            - llvm-toolchain-precise-3.8
+            - llvm-toolchain-trusty-6.0
           packages:
             - g++-5  # To install the dreaded `#include <codecvt>`.
-            - clang-3.8
+            - clang-6.0
+            - libstdc++-7-dev
             - nasm
             - gnuplot
 
@@ -63,17 +64,18 @@ matrix:
     - script: make individual_tests
       env:
       - NDEBUG=1
-      - CPLUSPLUS=clang++-3.8
-      compiler: "clang++-3.8, Job: make individual_tests"
+      - CPLUSPLUS=clang++-6.0
+      compiler: "clang++-6.0, Job: make individual_tests"
       os: linux
       addons:
         apt:
           sources:
             - ubuntu-toolchain-r-test  # `apt-get` on Travis fails to install `clang-3.6 gnuplot` w/o this.
-            - llvm-toolchain-precise-3.8
+            - llvm-toolchain-trusty-6.0
           packages:
             - g++-5  # To install the dreaded `#include <codecvt>`.
-            - clang-3.8
+            - clang-6.0
+            - libstdc++-7-dev
             - nasm
             - gnuplot
 
@@ -104,21 +106,22 @@ matrix:
     - script:
       - mkdir local_bin
       - ln -sf $(which g++-5) local_bin/g++
-      - ln -sf $(which clang++-3.8) local_bin/clang++
+      - ln -sf $(which clang++-6.0) local_bin/clang++
       - export PATH=$PWD/local_bin:$PATH
       - make check
       env:
       - MAKE_CHECK=1
-      compiler: "g++-5 && clang++-3.8, Job: make check"
+      compiler: "g++-5 && clang++-6.0, Job: make check"
       os: linux
       addons:
         apt:
           sources:
             - ubuntu-toolchain-r-test
-            - llvm-toolchain-precise-3.8
+            - llvm-toolchain-trusty-6.0
           packages:
             - g++-5
-            - clang-3.8
+            - clang-6.0
+            - libstdc++-7-dev
             - nasm
 
     - script: