Clone OpenGL-Registry submodule.

svenpanne · svenpanne · commit a9895c1c116d · 2018-03-21T17:57:46.000+01:00
diff --git a/.travis.yml b/.travis.yml
@@ -8,7 +8,7 @@ language: c
 sudo: false
 
 git:
-  submodules: false  # whether to recursively clone submodules
+  submodules: true  # whether to recursively clone submodules
 
 cache:
   directories:
