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/adb.c b/adb/adb.c
index d1f05e4..9c0bd8c 100644
--- a/adb/adb.c
+++ b/adb/adb.c
@@ -31,6 +31,7 @@
 #include "adb.h"
 #include "adb_auth.h"
 #include "adb_listeners.h"
+#include "transport.h"
 
 #define ARRAY_SIZE(a) (sizeof(a) / sizeof((a)[0]))