net-fixes: flow_dissector: prevent an infinite loop (CVE-2013-4348)

Jason Wang found that a malicious packet could make skb_flow_dissect()
loop forever. We must check that IP header has a valid ihl to avoid
this loop. It involves IPIP encapsulation and ihl = 0 to trigger.

Given this bug is critical, I cooked a patch before having
a fix in upstream kernel.

Tested:

 Compiled/booted
 Ran some tests on bnx2x and explicitely disabled hardware provided rxhash
 ethtool -K eth1 rxhash off
 ethtool -K eth2 rxhash off

Google-Bug-Id: 11465355
Effort: net-fixes
Change-Id: I813e4dc48cecb05f8edfa218304e1f13fd764323

Conflicts:
	net/core/flow_dissector.c
lib/memcopy: use glibc version

the kernel's memcpy and memmove is very inefficient. But the glibc version is
quite fast, in some cases it is 10 times faster than the kernel version. So I
introduce some memory copy macros and functions of the glibc to improve the
kernel version's performance.

The strategy of the memory functions is:
1. Copy bytes until the destination pointer is aligned.
2. Copy words in unrolled loops.  If the source and destination are not
   aligned in the same way, use word memory operations, but shift and merge
   two read words before writing.
3. Copy the few remaining bytes.

Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>
lib/string: use glibc version

The performance of memcpy and memmove of the general version is very
inefficient, this patch improved them.

Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>