remove <sys/timeb.h> for configure check

`ftime(3)` is depreacted POSIX API.
Since FreeBSD 9.0, compiler complains <sys/timeb.h> is deprecated:
"this file includes <sys/timeb.h> which is deprecated"

* OpenBSD no longer doesn't have this header.
    - removed libcompat at 2013/12/08
* NetBSD's header comment says deprecated, but no warnings during compilation.

It is only used in WIN32 environment.(Windows does not have `gettimeofday(2)`)