Enable _GLIBCXX_HAS_GTHREADS in GCC 4.8

Fix a test in libstdc++/confiugre to include $glibcxx_thread_h instead
of gthr.h otherwise it will fail to detect gthread lib because the
new gthr.h only include gthr-default.h which doesn't exist in source
directory

See issue http://code.google.com/p/android/issues/detail?id=41770
946c2a6b57ac7d3b2b656ac628bcb14a216ec635

Change-Id: I13bd69f45ddee8b38055f0264c8aa484df0761d2
Support OpenMP

See b6e375800c9a2f02a732cbdf5e87a860c3d954e1,
1271761f530c0050154e8d526b95f952df551751,
92c478dba755a1a2f6f00ff390666acbffd41982 and
51df2e98d22e2c6f5d2a16860bc8fc3644179c1d.

Change-Id: I7b01524a5516dd31b26a68cccc616a066893db39
Disable libstdc versioning

Used to be first half of NDK local patch at $NDK/build/tools/
toolchain-patches/gcc/0006-Disable-libstdc-versioning.patch

See 4a0927423d51f594b870e58b3eb51574327f8b0e

Change-Id: Ifc8efb661c5b4175feb1654fbc79525e1bc7f713
Use memalign instead of posix_memalign in GCC x86 mm_malloc.h

posix_memalign doesn't exist in NDK.  Code inludes ?mmintrin.h
which in turn includes mm_malloc.h may fail to link

For AOSP platform build which uses the same compiler, add
-DHAVE_POSIX_MEMALIGN to restore the original behavior.

Other than non-zero return value which _mm_alloc already ignores, both
paths are functioanlly identical (under the hood dlmalloc.c in 32-bit
ensure alignment is at least 16-byte)

See 0457b0db02c4b229eab11c01025df948032c31a7

Change-Id: I2e83d544a4ac2f4549de3b41a85e009a0a085476