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_auth.c b/adb/adb_auth.c
index 11a89b0..c236b64 100644
--- a/adb/adb_auth.c
+++ b/adb/adb_auth.c
@@ -24,6 +24,7 @@
 
 #include "adb.h"
 #include "adb_auth.h"
+#include "transport.h"
 #include "sysdeps.h"
 
 int auth_enabled = 0;