REORG: include: move pipe.h to haproxy/pipe{,-t}.h

No change was needed beyond a minor cleanup.
diff --git a/src/raw_sock.c b/src/raw_sock.c
index c1af72a..3c64d3c 100644
--- a/src/raw_sock.c
+++ b/src/raw_sock.c
@@ -32,7 +32,7 @@
 #include <haproxy/fd.h>
 #include <haproxy/freq_ctr.h>
 #include <proto/log.h>
-#include <proto/pipe.h>
+#include <haproxy/pipe.h>
 #include <proto/raw_sock.h>
 #include <proto/stream_interface.h>
 #include <proto/task.h>