compile:
$ clang -o hello hello.c -lX11 -lGL -lGLEW -L/usr/X11/lib -I/opt/X11/include
Result:
+------------------------------------------+
| Hello, World! [_][~][X]|
+------------------------------------------+
| |
| / \ |
| / \ |
| / \ |
| / \ |
| / \ |
| / \ |
| / \ |
| / \ |
| - - - - - - - - - - - - - - - - - |
+------------------------------------------+