switch to clang-format-3.8 (#2547)

https://llvm.org/bugs/show_bug.cgi?id=30353 was filed for the unintended
line break between in e.g. “TAILQ_ENTRY(foo)\nbar;”.

Until that’s fixed or a workaround is known, we’ll live with line
breaks. To make it a bit easier for readers to see what’s going on, I
added extra line breaks around each such struct member/variable
definition, so that they at least visually are a single unit.

fixes #2174

include/queue.h

@@ -446,7 +446,10 @@
     }
 
 #define CIRCLEQ_HEAD_INITIALIZER(head) \
-    { CIRCLEQ_END(&head), CIRCLEQ_END(&head) }
+    {                                  \
+        CIRCLEQ_END(&head)             \
+        , CIRCLEQ_END(&head)           \
+    }
 
 #define CIRCLEQ_ENTRY(type)                           \
     struct {                                          \