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/ipc.h

@@ -31,7 +31,8 @@ typedef struct ipc_client {
     int num_events;
     char **events;
 
-    TAILQ_ENTRY(ipc_client) clients;
+    TAILQ_ENTRY(ipc_client)
+    clients;
 } ipc_client;
 
 /*