Exclude compilers that don't come with kqueue headers on macOS.

.travis.yml

@@ -9,10 +9,13 @@ d:
   # this way the overall test time gets cut down (GDC/LDC are a lot
   # slower tham DMD, so they should be started early), while still
   # catching most DMD version related build failures early
-  - dmd-2.071.2
+  - dmd-2.073.0
   - dmd-2.070.2
+  - ldc-1.1.0-beta6
   - ldc-1.0.0
   - dmd-beta
+  - dmd-2.072.2
+  - dmd-2.071.2
 
 env:
     - CONFIG=select
@@ -28,6 +31,12 @@ matrix:
       env: CONFIG=epoll
     - os: linux
       env: CONFIG=kqueue
+    - os: osx
+      d: dmd-2.071.2
+    - os: osx
+      d: dmd-2.070.2
+    - os: osx
+      d: ldc-1.0.0
 
 script: ./travis-ci.sh