prebuilt kernel (selinux, tcp rwnd,  ping, usb disconnect) [DO NOT MERGE]

c594549 SELinux: Fix kernel BUG on empty security contexts.
686b8ed fix false disconnect due to a signal sent to the reading process
0a6c4e5 tcp: add a sysctl to config the tcp_default_init_rwnd
6917093 SELinux: Fix possible NULL pointer dereference in selinux_inode_permission()
8f9db83 nf: xt_qtaguid: fix handling for cases where tunnels are used.
e890ec8 ping: prevent NULL pointer dereference on write to msg_name
7dff567 SELinux: include definition of new capabilities

Bug: 12933504
Bug: 12765000
Bug: 12020135
Bug: 12905507
Bug: 11687690
Bug: 12780426
Bug: 11577088

Change-Id: I84a4e096084fa521594c5b4920870785e5394501
Merge "prebuilt kernel (selinux, tcp rwnd,  ping, usb disconnect) [DO NOT MERGE]" into android-4.4