Clear the IT state when invoking a Thumb-2 signal handler

If a process is interrupted during an If-Then block and a signal is
invoked, the ITSTATE bits must be cleared otherwise the handler would
not run correctly.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Joseph S. Myers <joseph@codesourcery.com>
Merge pull request #2 from vicamo/bugzilla/919901/emulator-thumb2-signal-handler

Bug 910901 - B2G Emulator: A signal dispatching bug in Linux 2.6.29. r=tlee
Backport of Seccomp-bpf ("mode filter") from Linux
kernel 3.8 and ChromiumOS "thirdparty" 3.4:
http://git.chromium.org/gitweb/?p=chromiumos/third_party/kernel.git

Conflicts:
	Documentation/filesystems/proc.txt
	arch/Kconfig
	arch/arm/Kconfig
	arch/arm/configs/C8666_defconfig
	arch/arm/kernel/entry-common.S
	arch/x86/ia32/ia32_signal.c
	fs/proc/array.c
	include/linux/Kbuild
	include/linux/audit.h
	include/linux/filter.h
	include/linux/prctl.h
	include/linux/sched.h
	include/linux/seccomp.h
	kernel/auditsc.c
	kernel/fork.c
	kernel/signal.c
	net/core/filter.c
	security/apparmor/domain.c
Check in a bunch of stuff so it builds.  It doesn't actually work.
Fake up a skb for the seccomp-bpf backport. It works now?

FIXME: In addition to being horrible, this probably violates strict aliasing.