[libcxx] r254050 - Silence a -Wmissing-braces warning in the tests; mbstate_t is defined differently on different C libraries.

[Joerg Sonnenberger via cfe-commits]

On Tue, Nov 24, 2015 at 05:38:23PM -0800, David Blaikie via cfe-commits wrote:
> Could this initialization just be written as "mbstate_t mb = {}" & avoid
> the warning entirely (I'm not entirely sure what the warning was, but I
> imagine that'd avoid it)

Or even better, just use the portable memset(&mb, 0, sizeof(mb)).

Joerg