Test against LLVM 3.8.1 instead of 3.8.0 in CI (ponylang#1366)

Author: Benoit Vey

.appveyor.yml

@@ -10,7 +10,7 @@ branches:
 environment:
   matrix:
   - llvm: 3.9.0
-  - llvm: 3.8.0
+  - llvm: 3.8.1
   - llvm: 3.7.1
 
 configuration:

.travis.yml

@@ -70,7 +70,7 @@ matrix:
           packages:
             - g++-5
       env:
-        - LLVM_VERSION="3.8.0"
+        - LLVM_VERSION="3.8.1"
         - LLVM_CONFIG="llvm-config-3.8"
         - config=debug
         - CC1=gcc-5
@@ -83,7 +83,7 @@ matrix:
           packages:
             - g++-5
       env:
-        - LLVM_VERSION="3.8.0"
+        - LLVM_VERSION="3.8.1"
         - LLVM_CONFIG="llvm-config-3.8"
         - config=release
         - CC1=gcc-5