Fix to use ucontext_t in unwind.h.

Fix to use ucontext_t in unwind.h.

ucontext_t is already defined in signal.h in the latest android
NDK. so it conflicts with defining _Unwind_Context ucontext_t.
this patch is for fixing the conflict by using tcmalloc namespace.

[JungJik, 2014-12-21 08:39:09]

jungjik.lee@samsung.com changed reviewers:
+ jar@chromium.org

[JungJik, 2014-12-21 08:39:10]

PTAL. thanks.

[JungJik, 2014-12-22 09:28:24]

jungjik.lee@samsung.com changed reviewers:
+ dmikurube@chromium.org

[JungJik, 2014-12-22 11:13:19]

On 2014/12/21 08:39:10, JungJik wrote:
> PTAL. thanks.

+ Dai Mikurube : PTAL thanks.

[Dai Mikurube (NOT FULLTIME), 2014-12-24 11:10:28]

It accepts both the current and older versions by using the namespace
tcmalloc::, right?  LGTM. (I'm not an OWNER of these two files, though.)

[JungJik, 2014-12-24 15:44:34]

On 2014/12/24 11:10:28, Dai Mikurube (NOT FULLTIME) wrote:
> It accepts both the current and older versions by using the namespace
> tcmalloc::, right?  LGTM. (I'm not an OWNER of these two files, though.)

yes. we are using the namespace. I think jar is resting.
we might need another owner of tcmalloc for merging and caring the latest vendor
code.
any way thanks Dai for the review and merry Christmas.