Move transport declarations into transport.h.

There are a few cloexec issues in here as an added bonus.

Change-Id: I1699d719d733f47878bdba0454230cf5ab6a60b6
diff --git a/adb_listeners.c b/adb_listeners.c
index cccc520..f68b876 100644
--- a/adb_listeners.c
+++ b/adb_listeners.c
@@ -20,6 +20,7 @@
 #include <stdlib.h>
 
 #include "sysdeps.h"
+#include "transport.h"
 
 int gListenAll = 0; /* Not static because it is used in commandline.c. */