Fix compile error on MINGW

Fixing compilation issue when compiling gtest-all.cc with MINGW (tested with x86_64-w64-mingw32-g++ (GCC) 4.8.3).

MINGW don't support neither localtime_s not localtime_r but localtime is thread safe in this case because on Windows localtime use a single tm structure per thread. (http://msdn.microsoft.com/en-us/library/bf12f0hc.aspx)

[Billy Donahue, 2015-01-05 16:39:42]

This is a good patch. I'm going to break out a little bit of separation between
the Localtime() and the formatting, just to make the portability noise more
contained.

[Billy Donahue, 2015-01-05 22:21:38]

On 2015/01/05 16:39:42, Billy Donahue wrote:
> This is a good patch. I'm going to break out a little bit of separation
between
> the Localtime() and the formatting, just to make the portability noise more
> contained.

How do you build on mingw? I'd like to verify my own version of this patch
locally.
Thanks.

[Tamas Berghammer, 2015-01-06 15:44:13]

On 2015/01/05 22:21:38, Billy Donahue wrote:
> On 2015/01/05 16:39:42, Billy Donahue wrote:
> > This is a good patch. I'm going to break out a little bit of separation
> between
> > the Localtime() and the formatting, just to make the portability noise more
> > contained.
> 
> How do you build on mingw? I'd like to verify my own version of this patch
> locally.
> Thanks.

I just building gtest-all.cc and gtest_main.cc with adding the proper include
directories (gtest and gtest/include).
I haven't figured out how to build the tests with mingw yet.