Disable aarch64/linux-unwind.h for now

Change-Id: I5ab969f1f7f049ebd043fe6e5a2b219c30338571

Author: Andrew Hsieh <andrewhsieh@google.com>
Date:   Tue Apr 9 17:01:52 2013 +0800
Update -mstack-protector-guard= support based on upstream comments

See http://gcc.gnu.org/ml/gcc-patches/2013-04/msg00764.html

Change-Id: I8aad144f579def5629fcb7cb29a68d057b809be2

Author: Andrew Hsieh <andrewhsieh@google.com>
Date:   Wed Apr 17 16:42:24 2013 +0800
Fix GNU4.7/4.8 libstdc++ for clang

Two fixes
1) Undefine GCC4.7/4.8 _GLIBCXX_ATOMIC_BUILTINS

   Clang arm/mips can't compile the following atomic intrinsics yet
     __atomic_fetch_add(__mem, __val, __ATOMIC_ACQ_REL);
     __atomic_fetch_add(__mem, __val, __ATOMIC_ACQ_REL);

   Use library calls instead

2) Undefine GCC4.7/4.8 _GLIBCXX_USE_FLOAT128.  Clang doesn't support
   __float128 yet

Change-Id: I0ff0eb208665beeb3e5e09917fd4c7dd378fc54e

Author: Andrew Hsieh <andrewhsieh@google.com>
Date:   Thu Apr 18 10:46:17 2013 +0800
Fix ARM/GCC-4.7,4.8 generates insufficient alignment for NEON vst/vld

GCC allocates memory buffer and passes it as the first hidden argument
for function return large composite type (ie. > 4 bytes for all NDK
toolchain).  Problem is that GCC doesn't observe the aligement
required by the type, and ARM EABI only requires stack to be aligned
to 8-byte.

Please see http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57271 for external
bug tracking this issue and testcase.  This CL offers temp relief before
formal one

Change-Id: I8004bc4208487e539ba8b0c9686c44ac86c37d83

Author: Andrew Hsieh <andrewhsieh@google.com>
Date:   Wed May 15 10:30:44 2013 +0800