Construct timeval in a way that MSVC likes
Construct timeval in a way that MSVC likes

Summary:
MSVC doesn't like it when you try to construct a struct by surrounding the type name with perenthesis, so remove the parenthesis and the unneeded struct keyword.
Closes https://github.com/facebook/fbthrift/pull/111

Reviewed By: juchem

Differential Revision: D2853352

Pulled By: Orvid

fb-gh-sync-id: 30df899cc012e11985626a177dec03dba5a917cd

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