headers: crt: Clean up time.h and sys/time.h

sys/time.h always include time.h, so no need to define timezone and
mingw_gettimeofday itself.

Use reserved parameter name for mingw_gettimeofday.

Remove _TIMEZONE_DEFINED and _GETTIMEOFDAY_DEFINED.

Signed-off-by: Zhongteng Gui <dragon-archer@outlook.com>
Signed-off-by: LIU Hao <lh_mouse@126.com>