libc: support __errno_location

Summary:
Android's errno behavior is the same as glibc's __errno_location.
Support __errno_location for compatibility.

Test Plan: verified fully

Reviewers: randall.rushing, synergy

Reviewed By: synergy

Differential Revision: http://review.codefirex.com/D236
[ARM] libc: optimized strnlen, strncat, strncmp, and strlcat

Summary:
Date:   Mon Sep 23 14:45:06 2013 -0700

    [ARM] libc: use basic ASM strnlen implementation

    Summary:
    This is based on the current naive strlen routine from
    netbsd

    Test Plan: significant implemented bench gains

    Reviewers: randall.rushing, synergy

    Reviewed By: synergy

    Differential Revision: http://review.codefirex.com/D499

    Conflicts:
        libc/Android.mk

Author: synergydev <synergye@codefi.re>
Date:   Mon Sep 23 14:43:27 2013 -0700

    [ARM] libc: use optimized ASM strncmp implementation

    Summary:
    This strncmp implementation is based on the current
    arm netbsd implementation

    Test Plan: https://sourceware.org/git/?p=glibc.git;a=blob;f=benchtests/bench-strncmp.c;h=25df3dbc2eb25346d9a897f8d7a2ada9725584e3;hb=master and integrated bionic-benchmark

    Reviewers: randall.rushing

Author: synergydev <synergye@codefi.re>
Date:   Sat Sep 21 23:45:58 2013 -0700

    [ARM] libc: use basic ASM strncat implementation

    Summary:
    This implementation is the naive strncat implementation
    for ARM from netbsd upstream.

    Test Plan: Someone else test please, bench gain is significant with http://repo.or.cz/w/glibc.git/blob_plain/ec901dcf2886cfb81d88f9a63cfcd62b9efe6381:/benchtests/bench-strncat.c (no currently integrated bench, only test which is good with this change).

    Reviewers: randall.rushing, ConnorBaker, synergy

    Reviewed By: synergy

Author: synergydev <synergye@codefi.re>
Date:   Mon Sep 23 14:42:47 2013 -0700

    [ARM] libc: use basic ASM strlcat implementation

    Summary: This is based on the netbsd naive strlcat implementation

    Test Plan: +1 here

    Reviewers: randall.rushing, synergy

    Reviewed By: synergy

Test Plan: significant implemented bench gains

Reviewers: randall.rushing, synergy

Reviewed By: synergy

Differential Revision: http://review.codefirex.com/D238

Conflicts:

	libc/Android.mk