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

src/ipc.c

@@ -22,7 +22,8 @@
 
 char *current_socketpath = NULL;
 
-TAILQ_HEAD(ipc_client_head, ipc_client) all_clients = TAILQ_HEAD_INITIALIZER(all_clients);
+TAILQ_HEAD(ipc_client_head, ipc_client)
+all_clients = TAILQ_HEAD_INITIALIZER(all_clients);
 
 /*
  * Puts the given socket file descriptor into non-blocking mode or dies if